Collector grid and interconnect structures for photovoltaic arrays and modules

ABSTRACT

An interconnected arrangement of photovoltaic cells is achieved using laminating current collector electrodes. The electrodes comprise a pattern of conductive material extending over a first surface of sheetlike substrate material. The first surface comprises material having adhesive affinity for a selected conductive surface. Application of the electrode to the selected conductive surface brings the first surface of the sheetlike substrate into adhesive contact with the conductive surface and simultaneously brings the conductive surface into firm contact with the conductive material extending over first surface of the sheetlike substrate. Use of the laminating current collector electrodes allows facile and continuous production of expansive area interconnected photovoltaic arrays.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 12/290,896 filed Nov. 5, 2008, entitled Collector Grid,Electrode Structures and Interconnect Structures for Photovoltaic Arraysand Methods of Manufacture, which is a Continuation-in-Part of U.S.patent application Ser. No. 11/824,047 filed Jun. 30, 2007, entitledCollector Grid, Electrode Structures and Interconnect Structures forPhotovoltaic Arrays and other Optoelectric Devices, which is aContinuation-in-Part of U.S. application Ser. No. 11/404,168 filed Apr.13, 2006, entitled Substrate and Collector Grid Structures forIntegrated Photovoltaic Arrays and Process of Manufacture of Such Arraysand now U.S. Pat. No. 7,635,810.

This application is also a Continuation-in-Part of U.S. patentapplication Ser. No. 12/798,221 filed Mar. 31, 2010 entitled CollectorGrid and Interconnect Structures for Photovoltaic Arrays and Modules,which is a Continuation-in-Part of U.S. patent application Ser. No.11/980,010 filed Oct. 29, 2007 entitled Collector Grid and InterconnectStructures for Photovoltaic Arrays and Modules.

This application is also a Continuation-in-Part of U.S. patentapplication Ser. No. 12/590,222 filed Nov. 3, 2009 entitled PhotovoltaicPower Farm Structure and Installation, which is a Continuation-in-Partof U.S. patent application Ser. No. 12/156,505 filed Jun. 2, 2008entitled Photovoltaic Power Farm Structure and Installation.

This application also claims priority to U.S. Provisional PatentApplication No. 61,274,960 filed Aug. 24, 2009 entitled Identification,Isolation, and Repair of Shunts and Shorts in Photovoltaic Cells.

The entire contents of the above identified applications areincorporated herein by this reference.

BACKGROUND OF THE INVENTION

Photovoltaic cells have developed according to two distinct methods. Theinitial operational cells employed a matrix of single crystal siliconappropriately doped to produce a planar p-n junction. An intrinsicelectric field established at the p-n junction produces a voltage bydirecting solar photon produced holes and free electrons in oppositedirections. Despite good conversion efficiencies and long-termreliability, widespread energy collection using single-crystal siliconcells is thwarted by the high cost of single crystal silicon materialand interconnection processing.

A second approach to produce photovoltaic cells is by depositing thinphotovoltaic semiconductor films on a supporting substrate. Materialrequirements are minimized and technologies can be proposed for massproduction. Thin film photovoltaic cells employing amorphous silicon,cadmium telluride, copper indium gallium diselenide, dye sensitizedpolymers and the like have received increasing attention in recentyears. Despite significant improvements in individual cell conversionefficiencies for both single crystal and thin film approaches,photovoltaic energy collection has been generally restricted toapplications having low power requirements. One factor impedingdevelopment of bulk power systems is the problem of economicallycollecting the energy from an extensive collection surface. Photovoltaiccells can be described as high current, low voltage devices. Typicallyindividual cell voltage is less than about two volts, and often lessthan 0.6 volt. The current component is a substantial characteristic ofthe power generated. Efficient energy collection from an expansivesurface must minimize resistive losses associated with the high currentcharacteristic. A way to minimize resistive losses is to reduce the sizeof individual cells and connect them in series. Thus, voltage is steppedthrough each cell while current and associated resistive losses areminimized.

It is readily recognized that making effective, durable seriesconnections among multiple small cells can be laborious, difficult andexpensive. In order to approach economical mass production of seriesconnected arrays of individual cells, a number of factors must beconsidered in addition to the type of photovoltaic materials chosen.These include the substrate employed and the process envisioned. Sincethin films can be deposited over expansive areas, thin film technologiesoffer additional opportunities for mass production of interconnectedarrays compared to inherently small, discrete single crystal siliconcells. Thus a number of U.S. patents have issued proposing designs andprocesses to achieve series interconnections among the thin filmphotovoltaic cells. Many of these technologies comprise deposition ofphotovoltaic thin films on glass substrates followed by scribing to formsmaller area individual cells. Multiple steps then follow toelectrically connect the individual cells in series array. Examples ofthese proposed processes are presented in U.S. Pat. Nos. 4,443,651,4,724,011, and 4,769,086 to Swartz, Turner et al. and Tanner et al.respectively. While expanding the opportunities for mass production ofinterconnected cell arrays compared with single crystal siliconapproaches, glass substrates must inherently be processed on anindividual batch basis.

More recently, developers have explored depositing wide area films usingcontinuous roll-to-roll processing. This technology generally involvesdepositing thin films of photovoltaic material onto a continuouslymoving web. However, a challenge still remains regarding subdividing theexpansive films into individual cells followed by interconnecting into aseries connected array. For example, U.S. Pat. No. 4,965,655 to Grimmeret. al. and U.S. Pat. No. 4,697,041 to Okamiwa teach processes requiringexpensive laser scribing and interconnections achieved with laser heatstaking. In addition, these two references teach a substrate of thinvacuum deposited metal on films of relatively expensive polymers. Theelectrical resistance of thin vacuum metallized layers significantlylimits the active area of the individual interconnected cells.

Many of the legacy techniques used to interconnect individualphotovoltaic cells into a modular format involve the use of low meltingpoint metal solders and/or electrically conductive adhesives. Thesetechniques are time consuming, expensive, and often require batchprocessing. Moreover, the electrical connections achieved with solderand/or electrically conductive adhesives have historically beensusceptible to deterioration when exposed to environmental or mechanicalstress.

It has become well known in the art that the efficiencies of certainpromising thin film photovoltaic junctions can be substantiallyincreased by high temperature treatments. These treatments involvetemperatures at which even the most heat resistant plastics suffer rapiddeterioration, thereby requiring either ceramic, glass, or metalsubstrates to support the thin film junctions. Use of a glass or ceramicsubstrates generally restricts one to batch processing and handlingdifficulty. Use of a metal foil as a substrate allows continuousroll-to-roll processing. However, despite the fact that use of a metalfoil allows high temperature processing in roll-to-roll fashion, thesubsequent interconnection of individual cells effectively in aninterconnected array has proven difficult, in part because the metalfoil substrate is electrically conducting.

U.S. Pat. No. 4,746,618 to Nath et al. teaches a design and process toachieve interconnected arrays using roll-to-roll processing of a metalweb substrate such as stainless steel. The process includes multipleoperations of cutting, selective deposition, and riveting. Theseoperations add considerably to the final interconnected array cost.

U.S. Pat. No. 5,385,848 to Grimmer teaches roll-to-roll methods toachieve integrated series connections of adjacent thin film photovoltaiccells supported on an electrically conductive metal substrate. Theprocess includes mechanical or chemical etch removal of a portion of thephotovoltaic semiconductor and transparent top electrode to expose aportion of the electrically conductive metal substrate. The exposedmetal serves as a contact area for interconnecting adjacent cells. Thesematerial removal techniques are troublesome for a number of reasons.First, many of the chemical elements involved in the best photovoltaicsemiconductors are expensive and environmentally unfriendly. Thisremoval subsequent to controlled deposition involves containment, dustand dirt collection and disposal, and possible cell contamination. Thisis not only wasteful but considerably adds to expense. Secondly, theremoval processes are difficult to control dimensionally. Thus asignificant amount of the valuable photovoltaic semiconductor is lost tothe removal process. Ultimate module efficiencies are furthercompromised in that the spacing between adjacent cells grows, therebyreducing the effective active collector area for a given module area.

Thus there remains a need for manufacturing processes and articles whichallow separate production of photovoltaic structures while also offeringunique means to achieve effective integrated connections.

A further unsolved problem which has thwarted production of expansivesurface photovoltaic modules is that of collecting the photogeneratedcurrent from the top, light incident surface. Transparent conductiveoxide (TCO) layers are normally employed as a top surface electrode.However, these TCO layers are relatively resistive compared to puremetals. Thus, efforts must be made to minimize resistive losses intransport of current through the TCO layer. One approach is simply toreduce the surface area of individual cells to a manageable amount.However, as cell widths decrease, the width of the area betweenindividual cells (interconnect area) should also decrease so that therelative portion of inactive surface of the interconnect area does notbecome excessive. Typical cell widths of one centimeter are often taughtin the art. These small cell widths demand very fine interconnect areawidths, which dictate delicate and sensitive techniques to be used toelectrically connect the top TCO surface of one cell to the bottomelectrode of an adjacent series connected cell. Furthermore, achievinggood stable ohmic contact to the TCO cell surface has proven difficult,especially when one employs those sensitive techniques available whenusing the TCO only as the top collector electrode. Another method is toform a current collector grid over the surface. This approach positionshighly conductive material in contact with the surface of the TCO in aspaced arrangement such that the travel distance of current through theTCO is reduced. In the case of the classic single crystal silicon orpolycrystal silicon cells, a common approach is to form a collector gridpattern of traces using a silver containing paste and then fuse thepaste to sinter the silver particles into continuous conductive silverpaths. These highly conductive traces normally lead to a collection busssuch as a copper foil strip. One notes that this approach involves useof expensive silver and requires the photovoltaic semiconductorstolerate the high fusion temperatures. Another approach is to attach anarray of fine copper wires to the surface of the TCO. The wires may alsolead to a collection buss, or alternatively extend to an electrode of anadjacent cell. This wire approach requires positioning and fixing ofmultiple fine fragile wires which makes mass production difficult andexpensive. Another approach is to print a collector grid array on thesurface of the TCO using a conductive ink, usually one containing aheavy loading of fine particulate silver. The ink is simply dried orcured at mild temperatures which do not adversely affect the cell. Theseapproaches require the use of relatively expensive inks because of thehigh loading of finely divided silver. In addition, batch printing onthe individual cells is laborious and expensive.

In a somewhat removed segment of technology, a number of electricallyconductive fillers have been used to produce electrically conductivepolymeric materials. This technology generally involves mixing of aconductive filler such as silver particles with the polymer resin priorto fabrication of the material into its final shape. Conductive fillersmay have high aspect ratio structure such as metal fibers, metal flakesor powder, or highly structured carbon blacks, with the choice based ona number of cost/performance considerations. More recently, fineparticles of intrinsically conductive polymers have been employed asconductive fillers within a resin binder. Electrically conductivepolymers have been used as bulk thermoplastic compositions, orformulated into paints and inks. Their development has been spurred inlarge part by electromagnetic radiation shielding and static dischargerequirements for plastic components used in the electronics industry.Other known applications include resistive heating fibers and batterycomponents and production of conductive patterns and traces. Thecharacterization “electrically conductive polymer” covers a very widerange of intrinsic resistivities depending on the filler, the fillerloading and the methods of manufacture of the filler/polymer blend.Resistivities for filled electrically conductive polymers may be as lowas 0.00001 ohm-cm. for very heavily filled silver inks, yet may be ashigh as 10,000 ohm-cm or even more for lightly filled carbon blackmaterials or other “anti-static” materials. “Electrically conductivepolymer” has become a broad industry term to characterize all suchmaterials. In addition, it has been reported that recently developedintrinsically conducting polymers (absent conductive filler) may exhibitresistivities comparable to pure metals.

In yet another separate technological segment, coating plasticsubstrates with metal electrodeposits has been employed to achievedecorative effects on items such as knobs, cosmetic closures, faucets,and automotive trim. The normal conventional process actually combinestwo primary deposition technologies. The first is to deposit an adherentmetal coating using chemical (electroless) deposition to first coat thenonconductive plastic and thereby render its surface highly conductive.This electroless step is then followed by conventional electroplating.ABS (acrylonitrile-butadiene-styrene) plastic dominates as the substrateof choice for most applications because of a blend of mechanical andprocess properties and ability to be uniformly etched. The overallplating process comprises many steps. First, the plastic substrate ischemically etched to microscopically roughen the surface. This isfollowed by depositing an initial metal layer by chemical reduction(typically referred to as “electroless plating”). This initial metallayer is normally copper or nickel of thickness typically one-halfmicrometer. The object is then electroplated with metals such as brightnickel and chromium to achieve the desired thickness and decorativeeffects. The process is very sensitive to processing variables used tofabricate the plastic substrate, limiting applications to carefullyprepared parts and designs. In addition, the many steps employing harshchemicals make the process intrinsically costly and environmentallydifficult. Finally, the sensitivity of ABS plastic to liquidhydrocarbons has prevented certain applications. ABS and other suchpolymers have been referred to as “electroplateable” polymers or resins.This is a misnomer in the strict sense, since ABS (and othernonconductive polymers) are incapable of accepting an electrodepositdirectly and must be first metallized by other means before beingfinally coated with an electrodeposit. The conventional technology forelectroplating on plastic (etching, chemical reduction, electroplating)has been extensively documented and discussed in the public andcommercial literature. See, for example, Saubestre, Transactions of theInstitute of Metal Finishing, 1969, Vol. 47, or Arcilesi et al.,Products Finishing, Mar. 1984.

Many attempts have been made to simplify the process of electroplatingon plastic substrates. Some involve special chemical techniques toproduce an electrically conductive film on the surface. Typical examplesof this approach are taught by U.S. Pat. No. 3,523,875 to Minldei, U.S.Pat. No. 3,682,786 to Brown et. al., and U.S. Pat. No. 3,619,382 toLupinski. The electrically conductive film produced was thenelectroplated. None of these attempts at simplification have achievedany recognizable commercial application.

A number of proposals have been made to make the plastic itselfconductive enough to allow it to be electroplated directly therebyavoiding the “electroless plating” process. It is known that one way toproduce electrically conductive polymers is to incorporate conductive orsemiconductive fillers into a polymeric binder. Investigators haveattempted to produce electrically conductive polymers capable ofaccepting an electrodeposited metal coating by loading polymers withrelatively small conductive particulate fillers such as graphite, carbonblack, and silver or nickel powder or flake. Heavy such loadings aresufficient to reduce volume resistivity to a level where electroplatingmay be considered. However, attempts to make an acceptableelectroplateable polymer using the relatively small metal containingfillers alone encounter a number of barriers. First, the most conductivefine metal containing fillers such as silver are relatively expensive.The loadings required to achieve the particle-to-particle proximity toachieve acceptable conductivity increases the cost of the polymer/fillerblend dramatically. The metal containing fillers are accompanied byfurther problems. They tend to cause deterioration of the mechanicalproperties and processing characteristics of many resins. Thissignificantly limits options in resin selection. All polymer processingis best achieved by formulating resins with processing characteristicsspecifically tailored to the specific process (injection molding,extrusion, blow molding, printing etc.). A required heavy loading ofmetal filler severely restricts ability to manipulate processingproperties in this way. A further problem is that metal fillers can beabrasive to processing machinery and may require specialized screws,barrels, and the like.

Another major obstacle involved in the electroplating of electricallyconductive polymers is a consideration of adhesion between theelectrodeposited metal and polymeric substrate (metal/polymer adhesion).In most cases sufficient adhesion is required to prevent metal/polymerseparation during extended environmental and use cycles. Despite beingelectrically conductive, a simple metal-filled polymer offers no assuredbonding mechanism to produce adhesion of an electrodeposit since themetal particles may be encapsulated by the resin binder, often resultingin a resin-rich “skin”.

A number of methods to enhance electrodeposit adhesion to electricallyconductive polymers have been proposed. For example, etching of thesurface prior to plating can be considered. Etching can be achieved byimmersion in vigorous solutions such as chromic/sulfuric acid.Alternatively, or in addition, an etchable species can be incorporatedinto the conductive polymeric compound. The etchable species at exposedsurfaces is removed by immersion in an etchant prior to electroplating.Oxidizing surface treatments can also be considered to improvemetal/plastic adhesion. These include processes such as flame or plasmatreatments or immersion in oxidizing acids. In the case of conductivepolymers containing finely divided metal, one can propose achievingdirect metal-to-metal adhesion between electrodeposit and filler.However, here the metal particles are generally encapsulated by theresin binder, often resulting in a resin rich “skin”. To overcome thiseffect, one could propose methods to remove the “skin”, exposing activemetal filler to bond to subsequently electrodeposited metal.

Another approach to impart adhesion between conductive resin substratesand electrodeposits is incorporation of an “adhesion promoter” at thesurface of the electrically conductive resin substrate. This approachwas taught by Chien et al. in U.S. Pat. No. 4,278,510 where maleicanhydride modified propylene polymers were taught as an adhesionpromoter. Luch, in U.S. Pat. No. 3,865,699 taught that certain sulfurbearing chemicals could function to improve adhesion of initiallyelectrodeposited Group VIII metals.

For the above reasons, electrically conductive polymers employing metalfillers have not been widely used as bulk substrates forelectroplateable articles. Such metal containing polymers have found useas inks or pastes in production of printed circuitry. Revived effortsand advances have been made in the past few years to accomplishelectroplating onto printed conductive patterns formed by silver filledinks and pastes.

An additional physical obstacle confronting practical electroplatingonto electrically conductive polymers is the initial “bridge” ofelectrodeposit onto the surface of the electrically conductive polymer.In electrodeposition, the substrate to be plated is often made cathodicthrough a pressure contact to a metal rack tip, itself under cathodicpotential. However, if the contact resistance is excessive or thesubstrate is insufficiently conductive, the electrodeposit currentfavors the rack tip to the point where the electrodeposit will notbridge to the substrate.

Moreover, a further problem is encountered even if specialized rackingor cathodic contact successfully achieves electrodeposit bridging to thesubstrate. Many of the electrically conductive polymers haveresistivities far higher than those of typical metal substrates. Also,many applications involve electroplating onto a thin (less than 25micrometer) printed substrate. The conductive polymeric substrate may berelatively limited in the amount of electrodeposition current which italone can convey. Thus, the conductive polymeric substrate does notcover almost instantly with electrodeposit as is typical with metallicsubstrates. Except for the most heavily loaded and highly conductivepolymer substrates, a large portion of the electrodeposition currentmust pass back through the previously electrodeposited metal growinglaterally over the surface of the conductive plastic substrate. In afashion similar to the bridging problem discussed above, theelectrodeposition current favors the electrodeposited metal and thelateral growth can be extremely slow and erratic. This restricts thesize and “growth length” of the substrate conductive pattern, increasesplating costs, and can also result in large non-uniformities inelectrodeposit integrity and thickness over the pattern.

This lateral growth is dependent on the ability of the substrate toconvey current. Thus, the thickness and resistivity of the conductivepolymeric substrate can be defining factors in the ability to achievesatisfactory electrodeposit coverage rates. When dealing withselectively electroplated patterns long thin metal traces are oftendesired, deposited on a relatively thin electrically conductive polymersubstrate. These factors of course often work against achieving thedesired result.

This coverage rate problem likely can be characterized by a continuum,being dependent on many factors such as the nature of the initiallyelectrodeposited metal, electroplating bath chemistry, the nature of thepolymeric binder and the resistivity of the electrically conductivepolymeric substrate. As a “rule of thumb”, the instant inventorestimates that coverage rate issue would demand attention if theresistivity of the conductive polymeric substrate rose above about 0.001ohm-cm. Alternatively, a “rule of thumb” appropriate for thin filmsubstrates would be that attention is appropriate if the substrate filmto be plated had a surface “sheet” resistance of greater than about 0.1ohm per square.

The least expensive (and least conductive) of the readily availableconductive fillers for plastics are carbon blacks. Attempts have beenmade to electroplate electrically conductive polymers using carbon blackloadings. Examples of this approach are the teachings of U.S. Pat. Nos.4,038,042, 3,865,699, and 4,278,510 to Adelman, Luch, and Chien et al.respectively.

Adelman taught incorporation of conductive carbon black into a polymericmatrix to achieve electrical conductivity required for electroplating.The substrate was pre-etched in chromic/sulfuric acid to achieveadhesion of the subsequently electroplated metal. A fundamental problemremaining unresolved by the Adelman teaching is the relatively highresistivity of carbon loaded polymers. The lowest “microscopicresistivity” generally achievable with carbon black loaded polymers isabout 1 ohm-cm. This is about five to six orders of magnitude higherthan typical electrodeposited metals such as copper or nickel. Thus, theelectrodeposit bridging and coverage rate problems described aboveremained unresolved by the Adelman teachings.

Luch in U.S. Pat. No. 3,865,699 and Chien et al. in U.S. Pat. No.4,278,510 also chose carbon black as a filler to provide an electricallyconductive surface for the polymeric compounds to be electroplated. TheLuch U.S. Pat. No. 3,865,699 and the Chien U.S. Pat. No. 4,278,510 arehereby incorporated in their entirety by this reference. However, theseinventors further taught inclusion of materials to increase the rate ofmetal coverage or the rate of metal deposition on the polymer. Thesematerials can be described herein as “electrodeposit growth rateaccelerators” or “electrodeposit coverage rate accelerators”. Anelectrodeposit coverage rate accelerator is a material functioning toincrease the electrodeposition coverage rate over the surface of anelectrically conductive polymer independent of any incidental affect itmay have on the conductivity of an electrically conductive polymer. Inthe embodiments, examples and teachings of U.S. Pat. Nos. 3,865,699 and4,278,510, it was shown that certain sulfur bearing materials, includingelemental sulfur, can function as electrodeposit coverage or growth rateaccelerators to overcome problems in achieving electrodeposit coverageof electrically conductive polymeric surfaces having relatively highresistivity or thin electrically conductive polymeric substrates havinglimited current carrying capacity.

In addition to elemental sulfur, sulfur in the form of sulfur donorssuch as sulfur chloride, 2-mercapto-benzothiazole,N-cyclohexyle-2-benzothiaozole sulfonomide, dibutyl xanthogen disulfide,and tetramethyl thiuram disulfide or combinations of these and sulfurwere identified. Those skilled in the art will recognize that thesesulfur donors are the materials which have been used or have beenproposed for use as vulcanizing agents or accelerators. Since thepolymer-based compositions taught by Luch and Chien et al. could beelectroplated directly they could be accurately defined as directlyelectroplateable resins (DER). These directly electroplateable resins(DER) can be generally described as electrically conductive polymerswith the inclusion of a growth rate accelerator.

Specifically for the present invention, specification, and claims,directly electroplateable resins, (DER), are characterized by thefollowing features:

-   -   (a) presence of an electrically conductive polymer;    -   (b) presence of an electrodeposit coverage rate accelerator;    -   (c) presence of the electrically conductive polymer and the        electrodeposit coverage rate accelerator in the directly        electroplateable composition in cooperative amounts required to        achieve direct coverage of the composition with an        electrodeposited metal or metal-based alloy.

In his Patents, Luch specifically identified unsaturated elastomers suchas natural rubber, polychloroprene, butyl rubber, chlorinated butylrubber, polybutadiene rubber, acrylonitrile-butadiene rubber,styrene-butadiene rubber etc. as suitable for the matrix polymer of adirectly electroplateable resin. Other polymers identified by Luch asuseful included polyvinyls, polyolefins, polystyrenes, polyamides,polyesters and polyurethanes.

When used alone, the minimum workable level of carbon black required toachieve “microscopic” electrical resistivities of less than 1000 ohm-cm.for a polymer/carbon black mix appears to be about 8 weight percentbased on the combined weight of polymer plus carbon black. The“microscopic” material resistivity generally is not reduced below about1 ohm-cm. by using conductive carbon black alone. This is several ordersof magnitude larger than typical metal resistivities.

It is understood that in addition to carbon blacks, other well known,highly conductive fillers can be considered in DER compositions.Examples include but are not limited to metallic fillers or flake suchas silver. In these cases the more highly conductive fillers can be usedto augment or even replace the conductive carbon black. Furthermore, onemay consider using intrinsically conductive polymers to supply therequired conductivity. In this case, it may not be necessary to addconductive fillers to the polymer.

The “bulk, macroscopic” resistivity of conductive carbon black filledpolymers can be further reduced by augmenting the carbon black fillerwith additional highly conductive, high aspect ratio fillers such asmetal containing fibers. This can be an important consideration in thesuccess of certain applications. Furthermore, one should realize thatincorporation of non-conductive fillers may increase the “bulk,macroscopic” resistivity of conductive polymers loaded with finelydivided conductive fillers without significantly altering the“microscopic resistivity” of the conductive polymer “matrix”encapsulating the non-conductive filler particles.

Regarding electrodeposit coverage rate accelerators, both Luch and Chienet al. in the above discussed U.S. patents demonstrated that sulfur andother sulfur bearing materials such as sulfur donors and vulcanizationaccelerators function as electrodeposit coverage rate accelerators whenusing an initial Group VIII metal electrodeposit “strike” layer. Thus,an electrodeposit coverage rate accelerator need not be electricallyconductive, but may be a material that is normally characterized as anon-conductor. The coverage rate accelerator need not appreciably affectthe conductivity of the polymeric substrate. As an aid in understandingthe function of an electrodeposit coverage rate accelerator thefollowing is offered:

-   -   a. A specific conductive polymeric structure is identified as        having insufficient current carrying capacity to be directly        electroplated in a practical manner.    -   b. A material is added to the conductive polymeric material        forming said structure. Said material addition may have        insignificant affect on the current carrying capacity of the        structure (i.e. it does not appreciably reduce resistivity or        increase thickness).    -   c. Nevertheless, inclusion of said material greatly increases        the speed at which an electrodeposited metal laterally covers        the electrically conductive surface.        It is contemplated that a coverage rate accelerator may be        present as an additive, as a species absorbed on a filler        surface, or even as a functional group attached to the polymer        chain. One or more growth rate accelerators may be present in a        directly electroplateable resin (DER) to achieve combined, often        synergistic results.

A hypothetical example might be an extended trace of conductive inkhaving a dry thickness of 1 micrometer. Such inks typically include aconductive filler such as silver, nickel, copper, conductive carbon etc.The limited thickness of the ink reduces the current carrying capacityof this trace thus preventing direct electroplating in a practicalmanner. However, inclusion of an appropriate quantity of a coverage rateaccelerator may allow the conductive trace to be directly electroplatedin a practical manner.

One might expect that other Group 6A elements, such as oxygen, seleniumand tellurium, could function in a way similar to sulfur. In addition,other combinations of electrodeposited metals, such as copper andappropriate coverage rate accelerators may be identified. It isimportant to recognize that such an electrodeposit coverage rateaccelerator is important in order to achieve direct electrodeposition ina practical way onto polymeric substrates having low conductivity orvery thin electrically conductive polymeric substrates having restrictedcurrent carrying ability.

It has also been found that the inclusion of an electrodeposit coveragerate accelerator promotes electrodeposit bridging from a discretecathodic metal contact to a DER surface. This greatly reduces thebridging problems described above.

Due to multiple performance problems associated with their intended enduse, none of the attempts identified above to directly electroplateelectrically conductive polymers or plastics has ever achieved anyrecognizable commercial success. Nevertheless, the current inventor haspersisted in personal efforts to overcome certain performancedeficiencies associated with the initial DER technology. Along withthese efforts has come a recognition of unique and eminently suitableapplications employing the DER technology. Some examples of these uniqueapplications for electroplated articles include solar cell electricalcurrent collection grids, electrodes, electrical circuits, electricaltraces, circuit boards, antennas, capacitors, induction heaters,connectors, switches, resistors, inductors, batteries, fuel cells,coils, signal lines, power lines, radiation reflectors, coolers, diodes,transistors, piezoelectric elements, photovoltaic cells, emi shields,biosensors and sensors. One readily recognizes that the demand for suchfunctional applications for electroplated articles is relatively recentand has been particularly explosive during the past decade.

It is important to recognize a number of important characteristics ofdirectly electroplateable resins (DERs) which facilitate the currentinvention. One such characteristic of the DER technology is its abilityto employ polymer resins and formulations generally chosen inrecognition of the fabrication process envisioned and the intended enduse requirements. In order to provide clarity, examples of some suchfabrication processes are presented immediately below in subparagraphs 1through 7.

-   -   (1) Should it be desired to electroplate an ink, paint, coating,        or paste which may be printed or formed on a substrate, a good        film forming polymer, for example a soluble resin such as an        elastomer, can be chosen to fabricate a DER ink (paint, coating,        paste etc.). For example, in some embodiments thermoplastic        elastomers having an olefin base, a urethane base, a block        copolymer base or a random copolymer base may be appropriate. In        some embodiments the coating may comprise a water based latex.        Other embodiments may employ more rigid film forming polymers.        The DER ink composition can be tailored for a specific process        such flexographic printing, rotary silk screening, gravure        printing, flow coating, spraying etc. Furthermore, additives can        be employed to improve the adhesion of the DER ink to various        substrates. One example would be tackifiers.    -   (2) Very thin DER traces often associated with collector grid        structures can be printed and then electroplated due to the        inclusion of the electrodeposit growth rate accelerator.    -   (3) Should it be desired to cure the DER substrate to a 3        dimensional matrix, an unsaturated elastomer or other “curable”        resin may be chosen.    -   (4) DER inks can be formulated to form electrical traces on a        variety of flexible substrates. For example, should it be        desired to form electrical structure on a laminating film, a DER        ink adherent to the sealing surface of the laminating film can        be effectively electroplated with metal and subsequently        laminated to a separate surface.    -   (5) Should it be desired to electroplate a fabric, a DER ink can        be used to coat all or a portion of the fabric intended to be        electroplated. Furthermore, since DER's can be fabricated out of        the thermoplastic materials commonly used to create fabrics, the        fabric itself could completely or partially comprise a DER. This        would eliminate the need to coat the fabric.    -   (6) Should one desire to electroplate a thermoformed article or        structure, DER's would represent an eminently suitable material        choice. DER's can be easily formulated using olefinic materials        which are often a preferred material for the thermoforming        process. Furthermore, DER's can be easily and inexpensively        extruded into the sheet like structure necessary for the        thermoforming process.    -   (7) Should one desire to electroplate an extruded article or        structure, for example a sheet or film, DER's can be formulated        to possess the necessary melt strength advantageous for the        extrusion process.    -   (8) Should one desire to injection mold an article or structure        having thin walls, broad surface areas etc. a DER composition        comprising a high flow polymer can be chosen.    -   (9) Should one desire to vary adhesion between an        electrodeposited DER structure supported by a substrate the DER        material can be formulated to supply the required adhesive        characteristics to the substrate. For example, the polymer        chosen to fabricate a DER ink can be chosen to cooperate with an        “ink adhesion promoting” surface treatment such as a material        primer or corona treatment. In this regard, it has been observed        that it may be advantageous to limit such adhesion promoting        treatments to a single side of the substrate. Treatment of both        sides of the substrate in a roll to roll process may adversely        affect the surface of the DER material and may lead to        deterioration in plateability. For example, it has been observed        that primers on both sides of a roll of PET film have adversely        affected plateability of DER inks printed on the PET. It is        believed that this is due to primer being transferred to the        surface of the DER ink when the PET is rolled up.

All polymer fabrication processes require specific resin processingcharacteristics for success. The ability to “custom formulate” DER's tocomply with these changing processing and end use requirements whilestill allowing facile, quality electroplating is a significant factor inthe teachings of the current invention.

Another important recognition regarding the suitability of DER's for theteachings of the current invention is the simplicity of theelectroplating process. Unlike many conventional electroplated plastics,DER's do not require a significant number of process steps prior toactual electroplating. This allows for simplified manufacturing andimproved process control. It also reduces the risk of crosscontamination such as solution dragout from one process bath beingtransported to another process bath. The simplified manufacturingprocess will also result in reduced manufacturing costs.

Another important recognition regarding the suitability of DER's for theteachings of the current invention is the wide variety of metals andalloys capable of being electrodeposited. Deposits may be chosen forspecific attributes. Examples may include copper for conductivity andnickel for corrosion resistance.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is the ability they offer to selectively electroplatean article or structure. The articles of the current invention oftenconsist of metal patterns selectively positioned in conjunction withinsulating materials. Such selective positioning of metals is oftenexpensive and difficult. However, the attributes of the DER technologymake the technology eminently suitable for the production of suchselectively positioned metal structures. As will be shown in laterembodiments, it is often desired to electroplate a polymer orpolymer-based structure in a selective manner. DER's are eminentlysuitable for such selective electroplating.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is the ability they offer to continuously electroplatean article or structure. As will be shown in later embodiments, it isoften desired to continuously electroplate articles. DER's are eminentlysuitable for such continuous electroplating. Furthermore, DER's allowfor selective electroplating in a continuous manner.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is their ability to withstand the pre-treatments oftenrequired to prepare other materials for plating. For example, were a DERto be combined with a metal, the DER material would be resistant to manyof the pre-treatments such as cleaning which may be necessary toelectroplate the metal.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is that the desired plated structure often requiresthe plating of long and/or broad surface areas. As discussed previously,the coverage rate accelerators included in DER formulations allow forsuch extended surfaces to be covered in a relatively rapid manner thusallowing one to consider the use of electroplating of conductivepolymers.

These and other attributes of DER's may contribute to successfularticles and processing of the instant invention. However, it isemphasized that the DER technology is but one of a number of alternativemetal deposition or positioning processes suitable to produce many ofthe embodiments of the instant invention. Other approaches, such aselectroless metal deposition or electroplating onto silver ink patternsmay be suitable alternatives. These choices will become clear in lightof the teachings to follow in the remaining specification, accompanyingfigures and claims.

In order to eliminate ambiguity in terminology, for the presentinvention the following definitions are supplied:

While not precisely definable, for the purposes of this specification,electrically insulating materials may generally be characterized ashaving electrical resistivities greater than 10,000 ohm-cm. Also,electrically conductive materials may generally be characterized ashaving electrical resistivities less than 0.001 ohm-cm. Alsoelectrically resistive or semi-conductive materials may generally becharacterized as having electrical resistivities in the range of 0.001ohm-cm to 10,000 ohm-cm. The characterization “electrically conductivepolymer” covers a very wide range of intrinsic resistivities dependingon the filler, the filler loading and the methods of manufacture of thefiller/polymer blend. Resistivities for electrically conductive polymersmay be as low as 0.00001 ohm-cm. for very heavily filled silver inks,yet may be as high as 10,000 ohm-cm or even more for lightly filledcarbon black materials or other “anti-static” materials. “Electricallyconductive polymer” has become a broad industry term to characterize allsuch materials. Thus, the term “electrically conductive polymer” as usedin the art and in this specification and claims extends to materials ofa very wide range of resitivities from about 0.00001 ohm-cm. to about10,000 ohm-cm and higher.

An “electroplateable material” is a material having suitable attributesthat allow it to be coated with a layer of electrodeposited material,either directly or following a preplating process.

A “metallizable material” is a material suitable to be coated with ametal deposited by any one or more of the available metallizing process,including chemical deposition, vacuum metallizing, sputtering, metalspraying, sintering and electrodeposition.

“Metal-based” refers to a material or structure having at least onemetallic property and comprising one or more components at least one ofwhich is a metal or metal-containing alloy.

“Alloy” refers to a substance composed of two or more intimately mixedmaterials.

“Group VIII metal-based” refers to a substance containing by weight 50%to 100% metal from Group VIII of the Periodic Table of Elements.

A “metal-based foil” or “bulk metal foil” refers to a thin structure ofmetal or metal-based material that may maintain its integrity absent asupporting structure. Generally, metal films of thickness greater thanabout 2 micrometers may have this characteristic (i.e. 2 micrometers, 10micrometers, 25 micrometers, 100 micrometers, 250 micrometers). Thus, inmost cases a “bulk metal foil” will have a thickness between about 2micrometers and 250 micrometers and may comprise a laminate of multiplelayers.

A “self supporting” structure is one that can be expected to maintainits integrity and form absent supporting structure.

A “film” refers to a thin material form having extended length and widthrelative to its thickness that may or may not be self supporting.

In this specification and claims, the terms “monolithic” or “monolithicstructure” are used as is common in industry to describe structure thatis made or formed from a single or uniform material. An example would bea “boat having a monolithic plastic hull”.

A “continuous” form of material is one that has a length dimension fargreater than its width or thickness such that the material can besupplied in its length dimension without substantial interruption.

A “continuous” process is one wherein a continuous form of a materialcomponent is supplied to the process. The material feed can be acontinuous motion or repetitively intermittent, and the output is timedto remove product either by continuous motion or repetitivelyintermittent according to the rate of input.

A “roll-to-roll” process is one wherein a material component is fed tothe process from a roll of material and the output of the process isaccumulated in a roll form.

The “machine direction” is that direction in which material istransported through a process step.

The term “multiple” is used herein to mean “two or more”.

A “web” is a thin, flexible sheetlike material form often characterizedas continuous in a length direction.

“Sheetlike” characterizes a structure having surface dimensions fargreater than the thickness dimension.

“Substantially planar” characterizes a surface structure which maycomprise minor variations in surface topography but from an overall andfunctional perspective can be considered essentially flat.

The terms “upper”, “upward facing”, and “top” surfaces of structurerefer to those surfaces of strictures facing upward in normal use. Forexample, when used to describe a photovoltaic device, an “upper” surfacerefers to that surface facing toward the sun.

The terms “lower”, “downward facing” or “bottom” surface refer tosurfaces facing away from an upward facing surface of the structure.

The term “cross-linked” indicates a polymer condition wherein chemicallinkages occur between chains. This condition typically results fromaddition of an agent intended to promote such linkages. Temperature andtime are normal parameters controlling the cross linking reaction.Accordingly, a thermoset adhesive is one whose reaction is acceleratedby increasing temperature to “set” or “cross-link” the polymer. Oftenthe term “curing” is used interchangeably with the term “cross-linking”.However, “curing” does not always necessarily mean “cross-linking”. A“cross-linked” polymer resists flow and permanent deformation and oftenhas considerable elasticity. However, since the molecules cannot flowover or “wet” a surface, the cross-linked polymer loses any adhesivecharacteristic. Rubber tire vulcanization is a quintessential example ofcross-linking.

The term “uncross-linked” is term describing a polymer having no crosslinks such that it retains its ability to be deformed and flowespecially at elevated temperatures. Often the word “thermoplastic’ isused to describe a “uncross-linked” polymer.

OBJECTS OF THE INVENTION

An object of the invention is to eliminate the deficiencies in the priorart methods of producing expansive area, series or parallelinterconnected photovoltaic arrays.

A further object of the present invention is to provide improvedsubstrates to achieve series or parallel interconnections amongphotovoltaic cells.

A further object of the invention is to provide structures useful forcollecting current from an electrically conductive surface.

A further object of the invention is to provide current collectorelectrode structures useful in facilitating mass production ofoptoelectric devices such as photovoltaic cell arrays.

A further object of the present invention is to provide improvedprocesses whereby interconnected photovoltaic arrays can be economicallymass produced.

A further object of the invention is to provide a process and means toaccomplish interconnection of photovoltaic cells into an integratedarray using continuous processing.

Other objects and advantages will become apparent in light of thefollowing description taken in conjunction with the drawings andembodiments.

SUMMARY OF THE INVENTION

The current invention provides a solution to the stated need byproducing the active photovoltaic cells and interconnecting structuresseparately and subsequently combining them to produce the desiredinterconnected array. One embodiment of the invention contemplatesdeposition of thin film photovoltaic junctions on metal foil substrateswhich may be heat treated following deposition if required in acontinuous fashion without deterioration of the metal support structure.In a separate operation, interconnection structures are produced. In anembodiment, interconnection structures are produced in a continuousroll-to-roll fashion. In an embodiment, the interconnecting structure islaminated to the metal foil supported photovoltaic cell and conductiveconnections are applied to complete the array. Furthermore, thephotovoltaic junction and its metal foil support can be produced inbulk. Subsequent application of a separate interconnection structureallows the interconnection structures to be uniquely formulated usingpolymer-based materials. Interconnections are achieved without the needto use the expensive and intricate material removal operations currentlytaught in the art to achieve interconnections.

In another embodiment, a separately prepared structure combining acurrent collector grid and interconnect portion is taught. In anembodiment the combined current collector/interconnect structure, alsoreferred to herein as a unit of interconnecting structure, is producedin a continuous roll-to-roll fashion. The current collector/interconnectstructure comprises conductive material positioned on a first surface ofa laminating sheet or positioning sheet which may be positioned inabutting contact with a conductive surface such as the light incidentsurface of a photovoltaic cell. The interconnect portion comprisesconductive material positioned on a second surface of the combinedstructure which may be positioned to abut the rear conductive surface ofanother photovoltaic cell.

BRIEF DESCRIPTION OF THE DRAWINGS

The various factors and details of the structures and manufacturingmethods of the present invention are hereinafter more fully set forthwith reference to the accompanying drawings wherein:

FIG. 1 is a top plan view of a thin film photovoltaic structureincluding its support structure.

FIG. 1A is a top plan view of the article of FIG. 1 following anoptional processing step of subdividing the article of FIG. 1 into cellsof smaller dimension.

FIG. 2 is a sectional view taken substantially along the line 2-2 ofFIG. 1.

FIG. 2A is a sectional view taken substantially along the line 2A-2A ofFIG. 1A.

FIG. 2B is a simplified sectional depiction of the structure embodied inFIG. 2A.

FIG. 2C is a simplified sectional view similar to FIG. 2A but alsoincluding additional insulating structure protecting raw cell edges.

FIG. 3 is an expanded sectional view showing a form of the structure ofsemiconductor 11 of FIGS. 2 and 2A.

FIG. 4 illustrates a possible process for producing the structure shownin FIGS. 1-3.

FIG. 5 is a sectional view illustrating the problems associated withmaking series connections among thin film photovoltaic cells shown inFIGS. 1-3.

FIG. 6 is a top plan view of a starting structure for an embodiment ofthe instant invention.

FIG. 7 is a sectional view, taken substantially along the lines 7-7 ofFIG. 6, illustrating a possible laminate structure of the embodiment.

FIG. 8 is a simplified sectional depiction of the FIG. 7 structuresuitable for ease of presentation of additional embodiments.

FIG. 9 is a top plan view of the structure embodied in FIGS. 6 through 8following an additional processing step.

FIG. 10 is a sectional view taken substantially from the perspective oflines 10-10 of FIG. 9.

FIG. 11 is a sectional view taken substantially from the perspective oflines 11-11 of FIG. 9.

FIG. 12 is a top plan view of an article resulting from exposing theFIG. 9 article to an additional processing step.

FIG. 13 is a sectional view taken substantially from the perspective oflines 13-13 of FIG. 12.

FIG. 14 is a sectional view taken substantially from the perspective oflines 14-14 of FIG. 12.

FIG. 15 is a sectional view taken substantially from the perspective oflines 15-15 of FIG. 12.

FIG. 15A is a view from a perspective similar to that of FIG. 15 byfollowing an additional optional processing step.

FIG. 16 is a top plan of an alternate embodiment similar in structure tothe embodiment of FIG. 9.

FIG. 17 is a sectional view taken substantially from the perspective oflines 17-17 of FIG. 16.

FIG. 17A is a sectional view similar to FIG. 15 showing an additionaloptional component included to prevent shorting during application tocells.

FIG. 18 is a sectional view taken substantially from the perspective oflines 18-18 of FIG. 16.

FIG. 19 is a simplified sectional view of the article embodied in FIGS.16-18 suitable for ease of clarity of presentation of additionalembodiments.

FIG. 20 is a sectional view showing the article of FIGS. 16 through 19following an additional optional processing step.

FIG. 20A is a view from a perspective similar to that of FIG. 20 butfollowing an additional optional processing step.

FIG. 20B is a view similar to FIG. 20A following combination of the FIG.20A structure with a photovoltaic cell.

FIG. 21 is a simplified depiction of a process useful in producingobjects of the instant invention.

FIG. 22 is a sectional view taken substantially from the perspective oflines 22-22 of FIG. 21 showing an arrangement of three components justprior to the Process 92 depicted in FIG. 21.

FIG. 23 is a sectional view showing the result of combining thecomponents of FIG. 22 using the process of FIG. 21.

FIG. 24 is a sectional view embodying a series interconnection ofmultiple articles as depicted in FIG. 23

FIG. 25 is an exploded sectional view of the region within the box “K”of FIG. 24.

FIG. 26 is a top plan view of a starting article in the production ofanother embodiment of the instant invention.

FIG. 27 is a sectional view taken from the perspective of lines 27-27 ofFIG. 26.

FIG. 28 is a simplified sectional depiction of the article of FIGS. 26and 27 useful in preserving clarity of presentation of additionalembodiments.

FIG. 29 is a top plan view of the original article of FIGS. 26-28following an additional processing step.

FIG. 30 is a sectional view taken substantially from the perspective oflines 30-30 of FIG. 29.

FIG. 31 is a sectional view of the article of FIGS. 29 and 30 followingan additional optional processing step.

FIG. 32 is a sectional view, similar to FIG. 22, showing an arrangementof articles just prior to combination using a process such as depictedin FIG. 21.

FIG. 33 is a sectional view showing the result of combining thearrangement depicted in FIG. 32 using a process as depicted in FIG. 21.

FIG. 34 is a sectional view a series interconnection of a multiple ofarticles such as depicted in FIG. 33.

FIG. 35 is a top plan view of a starting article used to produce anotherembodiment of the instant invention.

FIG. 35A is a top plan view of an embodiment of an alternate structure.

FIG. 36 is a simplified sectional view taken substantially from theperspective of lines 36-36 of FIG. 35.

FIG. 36A is a simplified sectional view taken substantially from theperspective of lines 36A-36A of FIG. 35A.

FIG. 37 is a expanded sectional view of the article embodied in FIGS. 35and 36 showing a possible multi-layered structure of the article.

FIG. 38 is a sectional view showing a structure combining repetitiveunits of the article embodied in FIGS. 35 and 36.

FIG. 39 is a top plan view of the article of FIGS. 35 and 36 followingan additional processing step.

FIG. 40 is a sectional view taken from the perspective of lines 40-40 ofFIG. 39.

FIG. 41 is a sectional view similar to that of FIG. 40 following anadditional optional processing step.

FIG. 41A is a sectional view like FIG. 41 but showing additionalstructure added to the embodiments of FIGS. 35A and 36A.

FIG. 42 is a sectional view showing a possible combining of the articleof FIG. 41 with a photovoltaic cell.

FIG. 43 is a sectional view showing multiple articles as in FIG. 42arranged in a series interconnected array.

FIG. 44 is a top plan view of a starting article in the production ofyet another embodiment of the instant invention.

FIG. 45 is a sectional view taken substantially from the perspective oflines 45-45 of FIG. 44 showing a possible layered structure for thearticle.

FIG. 46 is a sectional view similar to FIG. 45 but showing an alternatestructural embodiment.

FIG. 46A is a sectional view showing yet another alternate structuralembodiment.

FIG. 46B is a sectional view of the FIG. 46A structural embodiment afteraddition of another component.

FIG. 46C is a top plan view of another structural embodiment.

FIG. 46D is a sectional view of the structural embodiment of FIG. 46Ctaken substantially from the perspective of lines 46D-46D of FIG. 46C.

FIG. 46E is a sectional view of the embodiment of FIGS. 46C and 46Dafter addition of another component.

FIG. 46F is a top plan view of another embodiment.

FIG. 46G is a top plan view of the structural embodiment of FIG. 46Fafter adding an additional structural component.

FIG. 46H is a side view of the embodiment shown in FIG. 46G.

FIG. 47 is a simplified sectional view of the articles embodied in FIGS.44-46 useful in maintaining clarity and simplicity for subsequentembodiments.

FIG. 48 is a top plan view of the articles of FIGS. 44-46 and 47following an additional processing step.

FIG. 49 is a sectional view taken substantially from the perspective oflines 49-49 of FIG. 48.

FIG. 50 is a top plan view of the article of FIGS. 48 and 49 followingan additional processing step.

FIG. 51 is a sectional view taken substantially from the perspective oflines 51-51 of FIG. 50.

FIG. 52 is a sectional view of the article of FIGS. 50 and 51 followingan additional optional processing step.

FIG. 53 is a top plan view of an article similar to that of FIG. 50 butembodying an alternate structure.

FIG. 54 is a sectional view taken substantially from the perspective oflines 54-54 of FIG. 53.

FIG. 55 is a sectional view showing an article combining the article ofFIG. 52 with a photovoltaic cell.

FIG. 56 is a sectional view embodying series interconnection of multiplearticles as depicted in FIG. 55.

FIG. 57 is a top plan view of a structural arrangement as depicted inFIG. 56 but with some structural portions removed for clarity ofexplanation of a feature of the invention.

FIG. 58 is a sectional view taken substantially from the perspective oflines 58-58 of FIG. 57.

FIG. 59 is a sectional view embodying a possible condition when using acircular form in a lamination process.

FIG. 60 is a sectional view embodying a possible condition resultingfrom choosing a low profile form in a lamination process.

FIG. 61 is a top plan view embodying a possible process to achievepositioning of photovoltaic cells into a series interconnected array.

FIG. 62 is a perspective view of the process embodied in FIG. 61.

FIG. 63 is a top plan view of a modular array which may result from aprocess such as that of FIGS. 61 and 62. Thus, FIG. 63 may representstructure such as those presented in the sectional views of FIGS. 24,34, 43 and 56.

FIG. 64 is a depiction of the enclosed portion of FIG. 63 labeled “64portion” which shows additional structural detail.

FIG. 65 is a simplified sectional view taken substantially from theperspective of lines 65-65 of FIG. 64. Thus, FIG. 65 may representsimplified views of structure such as that presented in the sectionalviews of FIGS. 24, 34, 43 and 56.

FIG. 66 is a side view of a process wherein an array such as depicted inFIG. 65 may be applied to a protective sheet using roll lamination.

FIG. 67 is a sectional view taken substantially from the perspective oflines 67-67 of FIG. 66.

FIG. 68 is a sectional view showing the details of the layered structureresulting from a lamination process such as that of FIG. 66 wherein aprotective layer is applied an array such as that of FIGS. 63-65.

FIG. 69 is a top plan view showing a simplified depiction of structureuseful to explain a concept of the invention.

FIG. 70 is a sectional view taken substantially from the perspective oflines 70-70 of FIG. 69.

FIG. 71 is a replication of FIG. 15.

FIG. 72 shows the FIG. 71 structure following an optional process stepaccomplishing embedment of the conductive pattern into the substrate.

FIG. 73 is a view of the structure present in FIG. 20 but taken from theperspective such as that of FIG. 17.

FIG. 74 shows the structure of FIG. 73 following an optional processstep accomplishing embedment of the conductive pattern into thesubstrate.

FIG. 75 is a view similar to that of FIG. 20 after an optional embedmentprocess such as that embodied in FIGS. 72 and 74.

FIG. 76 is a view of the FIG. 75 embodiment but showing additional addedstructure.

FIG. 77 is a view similar to FIG. 76 showing one possible form ofinterconnecting structure.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals designate identical,equivalent or corresponding parts throughout several views and anadditional letter designation is characteristic of a particularembodiment.

Referring to FIGS. 1 and 2, an embodiment of a thin film photovoltaicstructure is generally indicated by numeral 1. It is noted here that“thin film” has become commonplace in the industry to designate certaintypes of semiconductor materials in photovoltaic applications. Theseinclude amorphous silicon, cadmium telluride, copper-indium-galliumdiselenide, dye sensitized polymers, so-called “Graetzel” electrolytecells and the like. While the characterization “thin film” may be usedto describe many of the embodiments of the instant invention, principlesof the invention may extend to photovoltaic devices not normallyconsidered “thin film” such as single crystal or polysilicon devices, asthose skilled in the art will readily appreciate. Structure 1 has alight-incident top surface 59 and a bottom surface 66. Structure 1 has awidth X-1 and length Y-1. It is contemplated that length Y-1 may beconsiderably greater than width X-1 such that length Y-1 can generallybe described as “continuous” or being able to be processed in aroll-to-roll fashion. FIG. 2 shows that structure 1 embodiment comprisesa thin film semiconductor structure 11 supported by “bulk” metal-basedfoil 12. Foil 12 has a top surface 65, bottom surface 66, and thickness“Z”. In the embodiment, bottom surface 66 of foil 12 also forms thebottom surface of photovoltaic structure 1. Metal-based foil 12 may beof uniform composition or may comprise a laminate of multiple layers.For example, foil 12 may comprise a base layer of inexpensive andprocessable metal 13 with an additional metal-based layer 14 disposedbetween base layer 13 and semiconductor structure 11. The additionalmetal-based layer 14 may be chosen to ensure good ohmic contact betweenthe top surface 65 of foil 12 and photovoltaic semiconductor structure11. Bottom surface 66 of foil 12 may comprise a material 75 chosen toachieve good electrical and mechanical joining characteristics as willbe shown. “Bulk” metal-based foil 12 is normally self supporting.Accordingly, the thickness “Z” of foil 12 is often between 2 micrometersand 250 micrometers (i.e. 5 micrometers, 10 micrometers, 25 micrometers,50 micrometers, 100 micrometers, 250 micrometers), although thicknessesoutside this range may be functional in certain applications. One notesfor example that should additional support be possible, such as thatsupplied by a supporting plastic film, metal foil thickness may be farless (0.1 to 1 micrometer) than those characteristic of a “bulk” foil.Nevertheless, a foil thickness between 2 micrometers and 250 micrometersmay normally provide adequate handling strength while still allowingflexibility if roll-to-roll processing were employed, as further taughthereinafter.

In its simplest form, a photovoltaic structure combines an n-typesemiconductor with a p-type semiconductor to from a p-n junction. Oftenan optically transparent “window electrode” such as a thin film of zincoxide or tin oxide is employed to minimize resistive losses involved incurrent collection.

FIG. 3 illustrates an example of a typical photovoltaic structure insection. In FIGS. 2 and 3 and other figures, an arrow labeled “hv” isused to indicate the light incident side of the structure. In FIG. 3, 15represents a thin film of a p-type semiconductor, 16 a thin film ofn-type semiconductor and 17 the resulting photovoltaic junction. Windowelectrode 18 completes a typical photovoltaic structure. The exactnature of the photovoltaic semiconductor structure 11 does not form thesubject matter of the present invention. For example, cells can bemultiple junction or single junction and comprise homo or heterojunctions. Semiconductor structure 11 may comprise any of the thin filmstructures known in the art, including but not limited to CIS, CIGS,CdTe, Cu2S, amorphous silicon, so-called “Graetzel” electrolyte cells,polymer based semiconductors and the like. Structure 11 may alsocomprise organic solar cells such as dye sensitized cells. Further,semiconductor structure 11 may also represent characteristically“non-thin film” cells such as those based on single crystal orpolycrystal silicon since many embodiments of the invention mayencompass such cells, as will be evident to those skilled in the art inlight of the teachings to follow.

In the following, photovoltaic cells having a metal based support foilwill be used to illustrate the embodiments and teachings of theinvention. However, those skilled in the art will recognize that many ofthe embodiments of the instant invention do not require the presence ofa “bulk” foil as represented in FIGS. 1 and 2. In many embodiments,other conductive substrate structures, such as a metallized polymer filmor glass having a thin metallized or conductive resin layer, may besubstituted for the “bulk” metal foil.

FIG. 4 refers to a method of manufacture of the bulk thin filmphotovoltaic structures generally illustrated in FIGS. 1 and 2. In theFIG. 4 embodiment, a “bulk” metal-based support foil 12 is moved in thedirection of its length Y through a deposition process, generallyindicated as 19. Process 19 accomplishes deposition of the activephotovoltaic structure onto foil 12. In the FIG. 4 embodiment, foil 12is unwound from supply roll 20 a, passed through deposition process 19and rewound onto takeup roll 20 b. As such, the process may becharacterized as a “roll-to-roll process. Process 19 can comprise any ofthe processes well-known in the art for depositing thin filmphotovoltaic structures. These processes include electroplating, vacuumevaporation and sputtering, chemical deposition, and printing ofnanoparticle precursors. Process 19 may also include treatments, such asheat treatments, intended to enhance photovoltaic cell performance.

Those skilled in the art will readily realize that the depositionprocess 19 of FIG. 4 may often most efficiently produce photovoltaicstructure 1 having dimensions far greater than those suitable forindividual cells in an interconnected array. Thus, the photovoltaicstructure 1 may be subdivided into cells 10 having dimensions X-10 andY-10 as indicated in FIGS. 1A and 2A for further fabrication. In FIG.1A, width X-10 defines a first photovoltaic cell terminal edge 45 andsecond photovoltaic cell terminal edge 46. In one embodiment, forexample, X-10 of FIG. 1A may be from 0.25 inches to 12 inches and Y-10of FIG. 1A may be characterized as “continuous”. In other embodimentsthe final form of cell 10 may be rectangular, such as 6 inch by 6 inch,4 inch by 3 inch or 8 inch by 2 inch. In other embodiments, thephotovoltaic structure 1 of FIG. 1 may be subdivided in the “X”dimension only thereby retaining the option of further processing in a“continuous” fashion in the “Y” direction. In the following, cellstructure 10 in a form having dimensions suitable for interconnectioninto a multi-cell array may be referred to as “cell stock” or simply ascells. “Cell stock” can be characterized as being either continuous ordiscreet.

FIG. 2B is a simplified depiction of cell 10 shown in FIG. 2A. In orderto facilitate presentation of the aspects of the instant invention, thesimplified depiction of cell 10 shown in FIG. 2B will normally be used.

FIG. 2C is a simplified depiction of cell 10 as in FIG. 2B but alsoshowing additional structure intended to protect a raw edge of the cellfrom shorting. In the FIG. 2C, a strip of insulating material 60 ispositioned along a cell edge. It has been found convenient to employstrips of a laminating film or pressure sensitive adhesive tape for theinsulating material. An adhesive layer 61 of the strip or tape ispositioned to overlap and contact a cell surface portion adjacent theedge, as shown in the drawing. A structural carrier layer 62 is alsonormally present to support the adhesive. The same process may be usedto protect the edge either from the top or bottom sides. Heat and/orpressure may be used to activate the adhesive of an insulatinglaminating film strip causing it to adhere to the cell surface as shownin the FIG. 2C. It has been found that a simple plastic bag sealer orimpulse sealer may be appropriate to accomplish this. Alternatively,simple room temperature application of a pressure sensitive adhesivetape (for example “Scotch Tape, a product of 3M Co.) has been usedeffectively. Raw edge protection is particularly appropriate when thinfilm photovoltaic cells are employed. In these cases, conductiveelectrical traces associated with current collection and cellinterconnection may extend across cell edges and thus may readily shortthe closely spaced top and bottom surfaces of a cell. In most of theembodiments to follow, the cell depiction of FIG. 2B will be used forsimplicity. However, one will understand that the FIG. 2B depiction ishighly simplified and does not include component structure nor the edgeprotection structure which would often be present in practice.

Referring now to FIG. 5, there are illustrated cells 10 as shown in FIG.2A. The cells have been positioned to achieve spatial positioning on thesupport substrate 21. Support structure 21 is by necessitynon-conductive at least in a space indicated by numeral 27 separatingthe adjacent cells 10. This insulating space prevents short circuitingfrom metal foil electrode 12 of one cell to foil electrode 12 of anadjacent cell. In order to achieve series connection, electricalcommunication must be made from the top surface of window electrode 18to the foil electrode 12 of an adjacent cell. This communication isshown in the FIG. 5 as a metal wire or tab 41. The direction of the netcurrent flow for the arrangement shown in FIG. 5 is indicated by thedouble pointed arrow “i”. It should be noted that foil electrode 12 isnormally relatively thin, on the order of 5 micrometer to 250micrometer. Therefore, connecting to its edge as indicated in FIG. 5would be impractical. Thus, such connections are normally made to thetop surface 65 or the bottom surface 66 of foil 12. One readilyrecognizes that connecting metal wire or tab 41 is laborious, makinginexpensive production difficult.

FIG. 6 is a top plan view of a starting article in production of alaminating current collector grid or electrode according to the instantinvention. FIG. 6 embodies a polymer based film or glassy substrate 70.Substrate 70 has width X-70 and length Y-70. In embodiments, taught indetail below, Y-70 may be much greater than width X-70, whereby film 70can generally be described as “continuous” in length and able to beprocessed in length direction Y-70 in a continuous roll-to-roll fashion.FIG. 7 is a sectional view taken substantially from the view 7-7 of FIG.6. Thickness dimension Z-70 is small in comparison to dimensions Y-70,X-70 and thus substrate 70 may have a flexible sheetlike, or webstructure contributing to possible roll-to-roll processing. Normally aflexible material can be significantly deformed and then returned tosubstantially its original shape. As shown in FIG. 7, substrate 70 maybe a laminate of multiple layers 72, 74, 76 etc. or may comprise asingle layer of material. Any number of layers 72, 74, 76 etc. may beemployed. The layers 72, 74, 76 etc. may comprise inorganic or organiccomponents such as thermoplastics, thermosets or silicon containingglass-like layers. As is understood in the art, a thermoplastic is apolymeric material which may be heated to make fluid without promoting aflow retarding chemical reaction. Also, as is understood in the art, athermoset is a material which may cure to a rigid or non-flowingmaterial when heated appropriately. The various layers are intended tosupply functional attributes such as environmental barrier protection oradhesive characteristics. Various PV barrier layers provide a number offunctional benefits including but not limited to protection from uvdegradation, water or moisture ingress, scratching etc. In addition, oneor more of the layers may be used to provide structural support duringprocessing and application. Such functional layering is well-known andwidely practiced in the plastic packaging art.

Sheetlike substrate 70 has first surface 80 and second surface 82. Inparticular, in light of the teachings to follow, one will recognize thatit may be advantageous to have layer 72 forming surface 80 comprise asealing or adhesive material such as an ethylene vinyl acetate (EVA),ethylene ethyl acetate (EEA), an ionomer, or a polyolefin based adhesiveto impart adhesive characteristics during a possible subsequentlamination process. Other sealing or adhesive materials useful incertain embodiments include those comprising atactic polyolefin, or apolymer containing polar functional groups for adhesive characteristicsduring a possible subsequent lamination process. Other sealing oradhesive materials useful in certain embodiments include thosecomprising silicones, silicone gels, epoxies, polydimethyl siloxane(PDMS), RTV rubbers, such as room temperature vulcanized silicones (RTVsilicones) polyvinyl butyral (PVB), thermoplastic polyurethanes (TPU),acrylics and urethanes. Both thermosetting and thermoplastic adhesiveshave been successfully employed in the practice of the invention.

The thickness of substrate 70, and specifically the thickness of thelayers such as layer 72 forming surface 80, may vary depending on therequirements imposed by subsequent processing or end use application.For example, for a subsequent roll lamination process the thickness oflayer 72 may typically be between 10 micrometers to 250 micrometers. Inroll lamination, sheetlike materials are heated and passed through a“nip” created by matched rollers. Pressure and heat applied by passingthrough the hot “nip” expels air between the sheets and laminates themtogether. Alternately, should a lamination process include encapsulationof relatively thick items such as “string and tab” arrangements ofcells, thicker layers from 100 micrometers to 600 micrometers may beemployed for layer 72. In this case vacuum lamination may be a preferredchoice of process.

Lamination of such sheetlike films employing such sealing materials is acommon practice in the packaging industry. In the packaging industrylamination is known and understood as applying a film, normally polymerbased and having a surface comprising a sealing material, to a secondsurface and sealing them together with heat and/or pressure. Sealingmaterials generally will have tacky or adhesive surfaces. Many suitablesealing materials may be made tacky and flowable, often under heatedconditions, and retain their adhesive bond to many surfaces uponcooling. A wide variety of laminating films with associated sealingmaterials is possible, depending on the surface to which the adhesiveseal or bond is to be made. Sealing materials such as olefin copolymersor atactic polyolefins may be advantageous, since these materials allowfor the minimizing of materials which may be detrimental to thelongevity of a solar cell with which it is in contact.

Additional layers 74, 76 etc. may comprise carrier materials whichsupply structural support for processing. A carrier material film istypically a structural polymer present to assist in overall integrity ofthe substrate. For example, the carrier film may structurally supportrelatively thin layers of an adhesive material which may not be selfsupporting absent the carrier. Typical carrier films comprise polymersupport layers and may include polypropylene, polyethylene terepthalate(PET), polyethylene naphthalate (PEN), acrylic, and polycarbonate.

Additional layers 74, 76 may comprise barrier materials such asfluorinated polymers, biaxially oriented polypropylene (BOPP),poly(vinylidene chloride), such as Saran, a product of Dow Chemical, andSiox. Saran is a tradename for poly (vinylidene chloride) and ismanufactured by Dow Chemical Corporation. Siox refers to a vapordeposited thin film of silicon oxide often deposited on a polymersupport. Siox can be characterized as an ultra thin glassy layer. Sioxis an example of many of the inorganic film structures being proposed asmoisture barrier materials for photovoltaic cells. Other examples ofvery thin flexible glass materials are those identified as Corning 0211and Schott D263. In addition, flexible transparent barrier sheetscontinue to be developed to allow production of flexible,environmentally secure photovoltaic modules. These more recent barriermaterials adopt the Siox concept but typically comprise stacks ofmultiple films in a laminar structure. The films may comprise multipleinorganic layers or combinations of multiple organic and inorganiclayers. The multiple layers present a tortuous path for moisture or gasmolecules to penetrate through the barrier sheet. The individual layersof the barrier sheet are typically very thin, often of the order of onemicrometer or less, formed by various processing such as sputtering,chemical vapor deposition and atomic layer deposition. Thus theseindividual layers are typically not self supporting. The barrier stackof multiple thin polymer and inorganic pairs (dyads) may be depositedonto a supporting carrier film which itself may be applied over a devicefor protection. An example of such a barrier film technology is thatmarketed by Vitex Systems under the tradename “Barix”. Additional layers74, 76 etc. may also comprise materials intended to afford protectionagainst ultraviolet radiation and may also comprise materials to promotecuring. The instant invention does not depend on the presence of anyspecific material for layers 72, 74, or 76. In many embodimentssubstrate 70 may be generally be characterized as a laminating material.For example, the invention has been successfully demonstrated usingstandard office laminating films of 75 micrometer and 150 micrometerthicknesses sold by GBC Corp., Northbrook, Ill., 60062. It has also beensuccessfully demonstrated using a 75 micrometer thick Surlyn adhesivelayer supported by a 50 micrometer thick polyethylene terepthalatecarrier film. It has also been successfully demonstrated using a 100micrometer thick olefinic adhesive layer supported by a 75 micrometerthick BOPP carrier film. It has also been successfully demonstratedusing 75 micrometer thick EVA adhesive layer supported by a 50micrometer thick polyethylene terepthalate carrier film. It has alsobeen successfully demonstrated using a 250 micrometer thick Surlynadhesive layer supported by a 50 micrometer thick polyethyleneterepthalate carrier film. Surlyn is a registered trademark for anionomer material sold by Dupont.

FIG. 8 depicts the structure of substrate 70 (possibly laminate) as asingle layer for purposes of presentation simplicity. Substrate 70 willbe represented as this single layer in the subsequent embodiments, butit will be understood that structure 70 may be a laminate of any numberof layers. In addition, substrate 70 is shown in FIGS. 6 through 8 ascomprising uniform, unvarying monolithic sheets. However, it isunderstood that various regions of substrate 70 may differ incomposition. For example, selected regions of substrate 70 may comprisediffering sheetlike structures patched together using appropriateseaming techniques. Possible applications for such a “patchwork”structure will become clear in light of the teachings to follow.

FIG. 9 is a plan view of the structure following an additionalmanufacturing step.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

FIG. 11 is a sectional view taken along line 11-11 of FIG. 9.

In the specific embodiments of FIGS. 9, 10, and 11, the structure is nowdesignated 71 to reflect the additional processing. It is seen that amaterial pattern has now been positioned on surface 80 of substrate 70.In the embodiments of FIGS. 9, 10, and 11, “fingers” or “traces” 84 and“busses” or “tabs” 86 are positioned on supporting substrate 70. Fingersor traces are arranged in a grid pattern comprising multiplesubstantially parallel traces. As shown in FIGS. 11 and 14, traces 84have a width Wt and a spacing St. Width Wt will typically correspond toa diameter if the trace comprises a wire as shown in FIG. 59. Tracewidth Wt (or wire diameter) is normally kept small to minimize shadingof the semiconductor. Typically width Wt is less than 375 micrometers(0.015 inch). The thickness of a typical trace (represented by “H” ofFIG. 13) is typically less than 300 micrometers (0.012 inch). Thespacing between parallel traces St is normally less than 0.5 inches(1.27 cm) in order to reduce resistive losses in lateral currenttransport over the conductive top surface of a photovoltaic cell.“Fingers” or “traces” 84 extend in the width X-71 direction of article71 from “busses” or “tabs” 86 extending in the Y-71 directionsubstantially perpendicular to the “fingers. As suggested above, article71 may be processed and extend continuously in the length “Y-71”direction. Repetitive multiple “finger/buss” arrangements are shown inthe FIG. 9 embodiment with a repeat dimension “F” as indicted. Portionsof substrate 70 not overlayed by “fingers” 84 and “busses” 86 remaintransparent or translucent to visible light. In the embodiment of FIGS.9 through 11, the “fingers” 84 and “busses” 86 are shown to be a singlelayer for simplicity of presentation. However, the “fingers” and“busses” can comprise multiple layers of differing materials chosen tosupport various functional attributes. For example the material indirect contact with substrate 70 defining the “buss” or “finger”patterns may be chosen for its adhesive affinity to surface 80 ofsubstrate 70 and also to a subsequently applied constituent of the bussor finger structure. Further, it may be advantageous to have the firstvisible material component of the fingers and busses be of dark color orblack. As will be shown, the light incident side (upper or outsidesurface) of the substrate 70 will eventually be surface 82. By havingthe first visible component of the fingers and busses be dark, they willaesthetically blend with the generally dark color of the photovoltaiccell. This eliminates the often objectionable appearance of a metalcolored grid pattern.

“Fingers” 84 and “busses” 86 may comprise electrically conductivematerial. Examples of such materials are metal wires and foils, stampedor die cut metal patterns, conductive metal containing inks and pastessuch as those having a conductive filler comprising silver or stainlesssteel, patterned deposited metals such as etched metal patterns ormasked vacuum deposited metals, intrinsically conductive polymers andDER formulations. In a preferred embodiment, the “fingers and “busses”comprise electroplateable material such as DER or an electricallyconductive ink which will enhance or allow subsequent metalelectrodeposition. “Fingers” 84 and “busses” 86 may also comprisenon-conductive material which would assist accomplishing a subsequentdeposition of conductive material in the pattern defined by the“fingers” and “busses”. For example, “fingers” 84 or “busses” 86 couldcomprise a polymer which may be seeded to catalyze chemical depositionof a metal in a subsequent step. An example of such a material is seededABS. Patterns comprising electroplateable materials or materialsfacilitating subsequent electrodeposition are often referred to as“seed” patterns or layers. “Fingers” 84 and “busses” 86 may alsocomprise materials selected to promote adhesion of a subsequentlyapplied conductive material. “Fingers” 84 and “busses” 86 may differ inactual composition and be applied separately. For example, “fingers” 84may comprise a conductive ink while “buss/tab” 86 may comprise aconductive metal foil strip. Alternatively, fingers and busses maycomprise a continuous unvarying monolithic material structure formingportions of both fingers and busses. Fingers and busses need not both bepresent in certain embodiments of the invention.

Permissible dimensions and structure for the “fingers” 84 and “busses”86 will vary somewhat depending on materials and fabrication processused for the fingers and busses, and the dimensions of the individualphotovoltaic cells. Moreover, “fingers” and “busses” may comprisematerial structure having dimensions, form or shape which may not beself supporting and may only be properly maintained using a supportingsubstrate such as sheetlike substrate 70. For example, one readilyrealizes that patterns of electrodeposited metal, ink traces, orpatterns of fine metal wires would likely demand additional support tomaintain pattern shape and material integrity.

One will recognize that while shown in the embodiments as a continuousvoid free surface, “buss” 86 could be selectively structured. Suchselective structuring may be appropriate to enhance functionality, suchas flexibility, of article 71 or any article produced there from.Furthermore, regions of substrate 70 supporting the “buss” regions 86may be different than those regions supporting “fingers” 84. Forexample, substrate 70 associated with “buss region” 86 may comprise afabric while substrate 70 may comprise a film devoid of thru-holes inthe region associated with “fingers” 84. A “holey” structure in the“buss region” would provide increased flexibility, increased surfacearea and increased structural characteristic for an adhesive to grip.Moreover, the embodiments of FIGS. 9 through 11 show the “fingers” and“busses” as essentially planar rectangular structures. Other geometricalforms are clearly possible, especially when design flexibility isassociated with the process used to establish the material pattern of“fingers” and “busses”. “Design flexible” processing includes printingof conductive inks or “seed” layers, foil etching or stamping, maskeddeposition using paint or vacuum deposition, and the like. For example,these conductive paths can have triangular type surface structuresincreasing in width (and thus cross section) in the direction of currentflow. Thus the resistance decreases as net current accumulates to reducepower losses. Alternatively, one may select more intricate patterns,such as a “watershed” pattern as described in U.S. Patent ApplicationPublication 2006/0157103 A1 which is hereby incorporated in its entiretyby reference. Various structural features, such as radiused connectionsbetween fingers and busses may be employed to improve structuralrobustness.

The embodiment of FIG. 9 shows multiple “busses” 86 extending in thedirection Y-71 with “fingers” extending from one side of the “busses” inthe X-71 direction. Many different such structural arrangements of thelaminating current collector structures are possible within the scopeand purview of the instant invention. It is important to note howeverthat many of the laminating current collector/interconnect structures ofthe instant invention may be manufactured utilizing continuous, bulkroll to roll processing. While the collector grid embodiments of thecurrent invention may advantageously be produced using continuousprocessing, one will recognize that combining of grids or electrodes soproduced with mating conductive surfaces may be accomplished usingeither continuous or batch processing. In one case it may be desired toproduce photovoltaic cells having discrete defined dimensions. Forexample, single crystal silicon cells are often produced having X-Ydimensions of approximately 6 inches by 6 inches. In this case thecollector grids of the instant invention, which may themselves beproduced continuously, may then be subdivided to dimensions appropriatefor combining with such cells. In other cases, such as production ofmany thin film photovoltaic structures, a continuous roll-to-rollproduction of an expansive surface article can be accomplished in the“Y” direction as identified in FIG. 1. Such a continuous expansivephotovoltaic structure may be combined with a continuous arrangement ofcollector grids of the instant invention in a semicontinuous orcontinuous manner. Alternatively the expansive semiconductor structuremay be subdivided into continuous strips of cell stock. In this case,combining a continuous strip of cell stock with a continuous strip ofcollector grid of the instant invention may be accomplished in acontinuous or semi-continuous manner.

FIGS. 12, 13 and 14 correspond to the views of FIGS. 9, 10 and 11respectively following an additional optional processing step. FIG. 15is a sectional view taken substantially along line 15-15 of FIG. 12.Such additional optional process steps accomplish improved function ofthe conductive patterns of the grid/interconnect structures of theinvention. For example, FIGS. 12 through 15 show additional conductivematerial deposited onto the “fingers” 84 and “busses” 86 of FIGS. 9through 11. In this embodiment additional conductive material isdesignated by one or more layers 88, 90. This additional conductivematerial enhances the current carrying capacity of the “fingers” and“busses”. Often when using “bulk” materials such as metal wires, stampedor etched metal foils and the like for the finger/buss pattern, thecurrent carrying capacity of the initial pattern “84/86” is adequate.However, when forming the conductive patterns using techniques such asprinting and metal electrodeposition, it may be desirable to enhancecurrent carrying ability above that supplied by the initial pattern“84/86”. For example, such enhancement may be appropriate as the lengthof fingers 84 increases.

While shown as two layers 88, 90, it is understood that this conductivematerial could comprise more than two layers or be a single layer. Inaddition, while each additional conductive layer is shown in theembodiment as having the same continuous monolithic material extendingover both the buss and finger patterns, one will realize that selectivedeposition techniques would allow the additional “finger” layers todiffer from additional “buss” layers. For example, as shown in FIG. 14,“fingers” 84 have free surface 98 and “busses” 86 have free surface 100.As noted, selective deposition techniques such as brush electroplatingor masked deposition would allow different materials to be consideredfor the “buss” surface 100 and “finger” surface 98. In a preferredembodiment, at least one of the additional layers 88, 90 etc. aredeposited by electrodeposition, taking advantage of the depositionspeed, compositional choice, low cost and selectivity of theelectrodeposition process. Many various metals, including highlyconductive silver, copper and gold, nickel, tin and alloys can bereadily electrodeposited. In these embodiments, it may be advantageousto utilize electrodeposition technology giving an electrodeposit of lowtensile stress to prevent curling and promote flatness of the metaldeposits. In particular, use of nickel deposited from a nickel sulfamatebath, nickel deposited from a bath containing stress reducing additivessuch as brighteners, or copper from a standard acid copper bath havebeen found particularly suitable. Electrodeposition also permits precisecontrol of thickness and composition to permit optimization of otherrequirements of the overall manufacturing process for interconnectedarrays. Thus, the electrodeposited metal may significantly increase thecurrent carrying capacity of the “buss” and “finger” structure and maybe the dominant current carrying material for these structures. Ingeneral, electrodeposit thicknesses characterized as “low profile”, lessthan about 0.002 inch, supply adequate current carrying capacity for thegrid “fingers” of the instant invention. Alternatively, these additionalconductive layers may be deposited by selective chemical deposition orregistered masked vapor deposition. These additional layers 88, 90 mayalso comprise conductive inks applied by registered printing.

As indicated in FIG. 13 the traces, fingers and busses project proudlyabove surface 80 of substrate 70 by dimension “H”. In many cases it maybe important to ensure that this projection is sufficient to assureadequate contacting of the surfaces 98, 100 with mating conductivesurfaces of a photovoltaic cell during lamination processing whichbrings the mating surfaces together. Specifically, during the laminationprocess heat and pressure may force the insulating material layer suchas 72 to melt and become fluid. Should the projection “H” beinsufficient, the laminating process may force insulating materialbetween the two mating conductive surfaces (such as 98 and 59).Sufficient projection “H” will force the mating conductive surfaces intofirm contact before insulating material can flow between them.

As will be discussed in more detail below, structures such as thatembodied in FIGS. 13-15 are combined with a mating conductive surfacesuch as upper surface 59 of photovoltaic cell 10. This combination isnormally achieved by laminating the structures together such thatsurface 80 and the conductive pattern thereupon face top surface 59 ofphotovoltaic cell 10 such that surfaces 98 and 100 of the patterncontact the conductive surface such as 59 of cell 10. Contact betweenthe top surface 59 of cell 10 and the mating surface 98 of finger 84will be achieved by ensuring good adhesion between surface 80 ofsubstrate 70 and surface 59 of cell 10.

In some cases it may be desirable to reduce the height of projection “H”prior to eventual combination with a conductive surface such as 59 or 66of photovoltaic cell 10. In other cases it may be desirable to improvethe coupling between the conductive pattern and the substrate 70.Suitable height reduction or increased coupling may be accomplished bypassing the structures as depicted in FIGS. 12-15 through a rolllamination process wherein pressurized and/or heated rollers embed“fingers” 84 and/or “busses” 86 into layer 72 of substrate 70. Dependingon the degree of heat and pressure and the nip spacing between rollers,the degree of the embedding (and residual projection “H”) can be closelycontrolled. In another embodiment, it has been demonstrated that asurface combining a conductive pattern embedded in a layer 72 ofsubstrate 70 can be made very smooth, showing a minimum of spatialdiscontinuity between the conductive and non-conductive surfaces. Such aunique surface could allow deposition of thin active semiconductorlayers directly onto a current collection grid without discontinuitiesat the edges of the grid traces.

For example, FIG. 71 shows a starting structure for such an embodimentof the instant invention. The FIG. 71 structure replicates the structureshown in FIG. 15. FIG. 73 shows the structure of FIG. 20 but from theperspective of FIG. 17. The sectional views of FIGS. 72 and 74 show theresult of embedding the conductive pattern into the substrate 70 or 70f.

The structure of FIG. 73 will be used to illustrate the use of thecurrent collector structures of the instant invention as a starting“superstrate” for subsequent deposition of semiconductor materialforming a photovoltaic stack. The process of this embodiment is asfollows:

-   -   1. A current collector/interconnect structure is first produced        as a pattern of electrically conductive material (84 f/86 f)        supported by a transparent sheetlike material 70 f. The        transparent sheetlike material 70 f may comprise glass or a        transparent polymeric material. In many cases a transparent        polymeric material is advantageous in that it may be processed        in continuous fashion.    -   2. Optionally, the FIG. 73 structure is passed through a        compressive step to imbed projecting pattern portions into the        underlying supporting substrate 70 f. The amount of the        “embedment” can be closely controlled using spaced nip rollers        and appropriate heat and pressure. In this case, patterns        supported on a flowable polymer may be advantageous in allowing        embedment, even to the point where the pattern and the substrate        are substantially “coplanar” and a very smooth surface        transition from substrate to pattern is achieved. Such a        coplanar structure is indicated in FIGS. 74 and 75.

3. Optionally, a transparent conductive material 18 is applied to thepatterned superstrate. This is shown in the embodiment of FIG. 76 usingthe perspective of the FIG. 75 sectional view. Such a material wouldoften be a transparent conductive metal oxide (TCO) as is known in theart. An alternative would be a transparent conductive materialcomprising an intrinsic conductive polymer. Yet another alternate wouldbe a material comprising a dispersion of transparent or small conductiveparticles in a resin matrix.

-   -   4. A layer of semiconductor material is deposited over the        transparent conductive material 15/16. Semiconductor material        15/16 forms a photovoltaic junction. Printing of the        semiconductors from appropriate inks is one form of process        allowing the selective deposition shown. Alternatively, masked        vapor deposition or electrodeposition onto the conductive TCO        surface may be considered for semiconductor deposition. In the        latter case the combination TCO/collector pattern would function        as a very effective electrode allowing expansive area        electrodeposition. Alternatively, the semiconductor material may        be deposited over the entire superstrate and portions        subsequently removed to result in the desired semiconductor        spatial arrangement.    -   5. Next a backside electrode 8 is deposited. This may be        accomplished by methods known in the art such as vacuum        deposition and printing of conductive inks.    -   6. As a next step, an interconnecting conductor 9 is applied        over the backside electrode 8. When interconnecting conductor 9        comprises a highly conductive material such as a metal foil, it        is noted that backside electrode 8 need not be highly        conductive, since backside electrode 8 may be very thin and area        expansive. In this case, one may consider inexpensive and easily        applied materials for the backside electrode 8. For example, 8        could comprise an adhesive film formulated using carbon black or        low levels of other conductive additive. The outlying portion 7        of interconnecting conductor 9 may be used to interconnect to an        adjacent photovoltaic stack.

When considering the above steps using the embodiments of FIGS. 71 and72, an important observation is that the entire production of anintegrated array of cells can be achieved monolithically (on amonolithic substrate) in a continuous fashion using a continuouspolymeric web. Process steps are primarily additive in nature.Subtractive steps envisioned do not demand great precision in materialremoval. Prior efforts at monolithic integration using a continuouspolymeric web have proven difficult because of the difficulty inachieving precise laser scribing on the flexible web. In addition,because of the absence of a topside current collector structure, priorefforts at photovoltaic structure deposition onto polymeric websuperstrates have been limited to relatively small cell widths of about1 centimeter. These small cell widths require increased precision inaccomplishing interconnections among cells.

Returning now to the discussion of the structure embodied in FIGS.13-15, it has been found very advantageous to form surface 98 of“fingers” 84 or surface 100 of “busses” 86 with a material compatiblewith the conductive surface with which eventual contact is made. Inpreferred embodiments, electroless deposition or electrodeposition isused to form a suitable metallic surface. Specifically electrodepositionoffers a wide choice of potentially suitable materials to form the freesurface. Corrosion resistant materials such as nickel, chromium, tin,indium, silver, gold and platinum are readily electrodeposited. Whencompatible, of course, surfaces comprising metals such as copper or zincor alloys of copper or zinc may be considered. Alternatively, thesurface 98 may comprise a conversion coating, such as a chromatecoating, of a material such as copper or zinc. Further, as will bediscussed below, it may be highly advantageous to choose a material toform surfaces 98 or 100 which exhibits adhesive or bonding ability to asubsequently positioned abutting conductive surface. For example, it maybe advantageous to form surfaces 98 and 100 using an electricallyconductive adhesive.

Alternatively, it may be advantageous to form surfaces 98 of “fingers 84and/or 100 of “busses” 86 with a conductive material such as a lowmelting point metal such as tin or tin containing alloys in order tofacilitate electrical joining to a complimentary conductive surfacehaving electrical communication with an electrode of an adjacentphotovoltaic cell. Such low melting point metals or alloys are oftenreferred to as solders. In this case the low melting point metal wouldbe chosen to have a melting point below a temperature reached duringprocessing such that surfaces 98 and/or 100 would become molten therebywet the complimentary conductive surface. Many plastic materials may beproperly processed at temperatures less than 600 degree Fahrenheit.Thus, for purposes of this specification and claims, a metal ormetal-based alloy whose melting point is less than 600 degree Fahrenheitis considered a low melting point metal. One will note that materialsforming “fingers” surface 98 and “buss” surface 100 need not be thesame. It is emphasized that many of the principles taught in detail withreference to FIGS. 6 through 15 extend to additional embodiments of theinvention taught in subsequent Figures.

FIG. 16 is a top plan view of an article 102 embodying another form ofthe electrodes of the current invention. FIG. 16 shows article 102having structure comprising a pattern of “fingers” or traces 84 aextending from “buss/tab” 86 a arranged on a substrate 70 a. Thestructure of FIG. 16 is similar to that shown in FIG. 9. However,whereas FIG. 9 depicted multiple finger and buss/tab structures arrangedin a substantially repetitive pattern in direction “X-71” on a commonsubstrate, the FIG. 16 embodiment consists of a single unit offinger/buss pattern. Thus, the dimension “X-102” of FIG. 16 may beroughly equivalent to the repeat dimension “F” shown in FIG. 9. Indeed,it is contemplated that article 102 of FIG. 16 may be produced bysubdividing the FIG. 9, structure 71 according to repeat dimension “F”shown in FIG. 9. Dimension “Y-102” may be chosen appropriate to theparticular processing scheme envisioned for the eventual lamination to aconductive surface such as a photovoltaic cell. However, it isenvisioned that “Y-102” may be much greater than “X-102” such thatarticle 102 may be characterized as continuous or capable of beingprocessed in a roll-to-roll fashion. Article 102 has a first terminaledge 104 and second terminal edge 106. In the FIG. 16 embodiment“fingers” 84 a are seen to terminate prior to intersection with terminaledge 106. One will understand that this is not a requirement.

“Fingers” 84 a and “buss/tab” 86 a of FIG. 16 have the samecharacterization as “fingers” 84 and “busses” 86 of FIGS. 9 through 11.Like the “fingers” 84 and “busses” 86 of FIGS. 9 through 11, “fingers”84 a and “buss” 86 a of FIG. 16 may comprise materials that are eitherconductive, assist in a subsequent deposition of conductive material orpromote adhesion of a subsequently applied conductive material tosubstrate 70 a. While shown as a single layer, one appreciates that“fingers” 84 a and “buss” 86 a may comprise multiple layers. Thematerials forming “fingers” 84 a and “buss” 86 a may be different or thesame. In addition, the substrate 70 a may comprise different materialsor structures in those regions associated with “fingers” 84 a and “bussregion” 86 a. For example, substrate 70 a associated with “buss region”86 a may comprise a fabric to provide thru-hole communication andenhance flexibility, while substrate 70 a in the region associated with“fingers” 84 a may comprise a film devoid of thru-holes such as depictedin FIGS. 6-8. A “holey” structure in the “buss region” would provideincreased flexibility, surface area and structural characteristic for anadhesive to grip.

It has been found very advantageous to form surface 98 a of “fingers” 84a or surface 100 a of “busses” 86 a with a material compatible with theconductive surface with which eventual contact is made. In preferredembodiments, electroless deposition or electrodeposition is used to forma suitable metallic surface. Specifically electrodeposition offers awide choice of potentially suitable materials to form the surface.Corrosion resistant materials such as nickel, chromium, tin, indium,silver, gold and platinum are readily electrodeposited. When compatible,of course, surfaces comprising metals such as copper or zinc or alloysof copper or zinc may be considered. Alternatively, the surfaces 98 aand 100 a may comprise a conversion coating, such as a chromate coating,of a material such as copper or zinc. Further, as will be discussedbelow, it may be highly advantageous to choose a material to formsurfaces 98 a or 100 a which exhibits adhesive or bonding ability to asubsequently positioned abutting conductive surface. For example, it maybe advantageous to form surfaces 98 a and 100 a using an electricallyconductive adhesive. Alternatively, it may be advantageous to formsurface 100 a of “busses” 86 a with a conductive material such as a lowmelting point alloy solder in order to facilitate electrical joining toa complimentary conductive surface associated with an electrode of anadjacent photovoltaic cell. For example, forming surfaces 98 a and 100 awith materials such as tin or alloys of tin with an alloying elementsuch as lead, bismuth or indium would result in a low melting pointsurface to facilitate electrical joining during subsequent laminationsteps. One will note that materials forming “fingers” surface 98 a and“buss” surface 100 a need not be the same.

Another alternative embodiment of the laminated electrodes of theinstant invention, particularly suitable for photovoltaic application,employs a film of transparent conductive or semi-conductive material tofurther enhance adhesion and contact of the highly conductive patternsto a complimentary surface. In this case, a transparent conductivematerial is positioned between the pattern and the complimentarysurface. In the embodiment of FIG. 20A, a transparent electricallyconductive material layer 95 has been applied over both the conductivepattern (84 c/86 c) and the regions of substrate positioned betweenpattern portions. In this case the FIG. 20A structure may be applied tothe upper surface of a photovoltaic cell because layer 95 istransparent. A similar arrangement is shown for a repetitive structurein FIG. 15A.

Transparent conductive or semi-conductive material 95 may be appliedover the conductive pattern (84 c/86 c) and supporting substrate 70 cusing standard lamination processing should material 95 be presented asa film. Alternatively, material 95 may be applied as a dissolved solidin solution using standard spray, doctor blade or printing techniques.Transparent conductive material 95 may comprise transparent conductiveparticles dispersed in a resin matrix. Transparent conductive particlesmay comprise, for example, metal oxides such as zinc oxide or indium-tinoxide. Alternatively, conductive particles may comprise intrinsicallyconductive polymers. Alternatively, small volume percentages of smalldiameter metal fibers or particles may be employed without introducingexcessive shading through the material thickness. Combinations oftransparent and opaque conductive particles may be considered.

A resin binder for material 95 may be chosen to have adhesive affinityfor both the substrate surface 80 a and light incident top surface 59 ofthe photovoltaic cell 10. In this case conductive or semi-conductivematerial 95 can be considered a transparent conductive orsemi-conductive adhesive bonding the substrate/pattern stack to thesurface of the photovoltaic cell.

Transparent conductive material 95 may be applied to either the lightincident top surface 59 of a photovoltaic cell or to the substratesurface 80A and pattern as shown in FIG. 20A. In the former case,material 95 may augment a characteristic of an underlying TCO, such asto impart an adhesive ability or protective barrier. In the later casethe transparent conductive material may be applied to the laminatingsubstrate as a step in continuous production.

The intrinsic resistivity of the transparent conductive material may berelatively high, for example of the order 1 ohm-cm. or even higher. Thisis because the transparent conductive or semi-conductive material neednot contribute in a significant way to lateral conductivity on the lightincident surface 59 of the photovoltaic cell. There, lateral surfaceconductivity is primarily managed by the application of the TCO layer18. The material 95 need only transport current through a very thinlayer (typically 1-12 micrometer) and over a relatively broad surfacedefined by the conductive pattern. Since there is not a requirement forhigh conductivity for the material 95, the actual volume loading ofconductive particles (in the case of resin dispersed particles) can bereduced to thereby increase light transmission.

FIG. 20B shows an embodiment of a possible structural stack employingthe FIG. 20A structure applied to the upper surface 59 of a photovoltaiccell 10. Application may be by straightforward lamination of the FIG.20A structure to the upper surface of a photovoltaic cell 10.

FIGS. 17 and 18 are sectional embodiments taken substantially from theperspective of lines 17-17 and 18-18 respectively of FIG. 16. FIGS. 17and 18 show that article 102 has thickness Z-102 which may be muchsmaller than the X and Y dimensions, thereby allowing article 102 to beflexible and processable in roll form. Also, flexible sheet-like article102 may comprise any number of discrete layers (three layers 72 a, 74 a,76 a are shown in FIGS. 17 and 18). These layers contribute tofunctionality as previously pointed out in the discussion of FIG. 7. Aswill be understood in light of the following discussion, it is normallyhelpful for layer 72 a forming free surface 80 a to exhibit adhesivecharacteristics to the eventual abutting conductive surface.

FIG. 17A is a sectional view showing additional structure 68 applied tothe FIG. 17 embodiment. Structure 68 comprises an insulating strip ortape spanning the intersection of “fingers” 84 a and “buss” 86 a. Aswill be seen in the teachings to follow, it is this region where theconductive traces normally cross an edge of a photovoltaic cell. Thusthe strip 68 prevents shorting caused by incidental contact of a tracewith both the top and bottom surfaces of a cell. The strip of tapecomprises an adhesive layer 64 and carrier layer 63 as is common withpressure sensitive tapes or laminating sheets.

FIG. 19 is an alternate representation of the sectional view of FIG. 18.FIG. 19 depicts substrate 70 a as a single layer for ease ofpresentation. The single layer representation will be used in manyfollowing embodiments, but one will understand that substrate 70 a maycomprise multiple layers.

FIG. 20 is a sectional view of the article now identified as 110,similar to FIG. 19, after an additional optional processing step. In afashion like that described above for production of the currentcollector structure of FIGS. 12 through 15, additional conductivematerial (88 a/90 a) has been deposited by optional processing toproduce the article 110 of FIG. 20. The discussion involving processingto produce the article of FIGS. 12 through 15 is proper to describeproduction of the article of FIG. 20. Thus, while additional conductivematerial has been designated as a single layer (88 a/90 a) in the FIG.20 embodiment, one will understand that layer (88 a/90 a) of FIG. 20 mayrepresent any number of multiple additional layers. In subsequentembodiments, additional conductive material (88 a/90 a) will berepresented as a single layer for ease of presentation. In its formprior to combination with cells 10, the structures such as shown inFIGS. 9-15, and 16-20 can be referred to as “current collector stock”.For the purposes of this specification and claims a current collector inits form prior to combination with a conductive surface can be referredto as “current collector stock”. Articles 102 and 110 may becharacterized as a unit of “current collector stock”. Moreover, “currentcollector stock” can be in either continuous or discrete form. Further,in light of the teachings to follow one will recognize that thestructures shown in FIGS. 9-15 and 16-20 may function and becharacterized as laminating electrodes.

FIG. 21 illustrates a process 92 by which the current collector grids ofFIGS. 16 through 20 may be combined with the structure illustrated inFIGS. 1A, 2A and 2B to accomplish lamination of current collectingelectrodes to top and bottom surfaces photovoltaic cell stock. Theprocess envisioned in FIG. 21 has been demonstrated using standardlamination processing such as roll lamination and vacuum lamination. Ina preferred embodiment, roll lamination is employed. In roll lamination,sheetlike feed streams are fed to a nip formed by a pair of rollers.Heat and pressure applied when passing through the hot nip expels airand bonds the sheetlike surfaces together.

Roll lamination allows continuous processing and a wide choice ofapplication temperatures and pressures. However, the rapid processingafforded by roll lamination places limits on the thicknesses of the feedstreams because of the rapid heating rates involved. Moreover, rolllamination requires adequate structural integrity of the feed streams.This is especially true when continuous lamination is involved. Thusroll lamination will typically involve a relatively thin adhesivesealing material layer supported on a structural polymeric carrier film.Roll lamination is further characterized as allowing relatively shortthermal exposure. This is an advantage in processing throughput and alsoin some instances may avoid thermal semiconductor deterioration.However, such short thermal exposures (rapid heat up and cool down)normally require relatively thin materials. For example, using rolllamination the total thickness of a sealing layer would typically beless than 250 micrometers (i.e. 75 micrometers, 150 micrometers, 200micrometers). A complimentary carrier layer would typically be less than125 micrometers (i.e. 50 micrometers, 100 micrometers). In contrast,many of the legacy encapsulation techniques for solar cell module employsealing materials in excess of 375 micrometers. Such thick materialsrequire extended batch processing such as that characteristic of vacuumlamination processing.

Temperatures employed for process 92 of FIG. 21 are typical forlamination of standard polymeric materials used in the high volumeplastics packaging industry, normally less than about 500 degreesFahrenheit. Process 92 is but one of many processes possible to achievesuch application. In FIG. 21 rolls 94 and 97 represent “continuous” feedrolls of grid/buss structure on a flexible sheetlike substrate (currentcollector stock) as depicted in FIGS. 16 through 20. Roll 96 representsa “continuous” feed roll of the sheetlike cell stock as depicted inFIGS. 1A, 2A and 2B.

FIG. 22 is a sectional view taken substantially from the perspective ofline 22-22 of FIG. 21. FIG. 22 shows a photovoltaic cell 10 such asembodied in FIGS. 2A and 2B disposed between two current collectingelectrodes 110 a and 110 b such as article 110 embodied in FIG. 20. FIG.23 is a sectional view showing the article 112 resulting from usingprocess 92 to laminate the three individual structures of FIG. 22 whilesubstantially maintaining the relative positioning depicted in FIG. 22.FIG. 23 shows that a laminating current collector electrode 110 a hasnow been applied to the top conductive surface 59 of cell 10. The gridpattern of “fingers” or traces 84 a extends over a preponderance of thelight incident surface 59 of cell 10. Laminating current collectorelectrode 110 b mates with and contacts the bottom conductive surface 66of cell 10. Grid “fingers” 84 a of a current collector electrode 110 aproject laterally across the top surface 59 of cell stock 10 and extendto a “buss” region 86 a located outside terminal edge 45 of cell stock10. The grid “fingers” 84 a of a bottom current collector electrode 110b project laterally across the bottom surface 66 of cell stock 10 andextend to a “buss” region 86 a located outside terminal edge 46 of cellstock 10. Thus article 112 is characterized as having readily accessibleconductive surface portions 100 a in the form of tabs in electricalcommunication with both top cell surface 59 and bottom cell surface 66.

Those skilled in the art will recognize that contact between the topsurface 59 of cell 10 and the mating surface 98 a of finger 84 a will beachieved by ensuring good adhesion between surface 80 a of substrate 70a and surface 59 of cell 10. One will further recognize that contactbetween bottom surface 66 of cell 10 and fingers 84 a of collector grid110 b will be ensured by achieving adhesion between surface 80 a ofsubstrate 70 a and surface 66 of cell 10. In particular, the materialforming the remaining free surface 80 a of articles 110 a and 110 b(that portion of surfaces 80 a not covered with conductive material) ischosen to promote good adhesion between articles 110 a and 110 b and thecorresponding cell surfaces during a laminating process. Thus, in theembodiment of FIGS. 22 and 23 surface 80 a comprises material havingadhesive affinity to both surfaces 59 and 66 of cell 10.

Article 112 can be described as a “tabbed cell stock”. In the presentspecification and claims, a “tabbed cell stock” is defined as aphotovoltaic cell structure combined with electrically conductingmaterial in electrical communication with a conductive surface of thecell structure, and further wherein the electrically conducting materialextends outside a terminal edge of the cell structure to present areadily accessible contact surface. In light of the present teachings,one will understand that “tabbed cell stock” can be characterized asbeing either continuous or discrete. One will also recognize thatelectrodes 110 a and 110 b can be used independently of each other. Forexample, 110 b could be employed as a back side electrode while acurrent collector electrode different than 110 a is employed on theupper side of cell 10. Also, one will understand that while electrodes110 a and 110 b are shown in the embodiment to be the same structure,different structures and compositions may be chosen for electrodes 110 aand 110 b.

A “tabbed cell stock” 112 has a number of fundamental advantageousattributes. First, it can be produced as a continuous cell “strip” andin a continuous roll-to-roll fashion in the Y direction (directionnormal to the paper in the sectional view of FIG. 23). Following theenvisioned lamination, the “tabbed cell stock” strip can be continuouslymonitored for quality since there is ready access to the exposed freesurfaces 100 a in electrical communication with top cell surface 59 andthe cell bottom surface 66. Thus defective cell material can beidentified and discarded prior to final interconnection into an array.Finally, the laminated current collector electrodes protect the surfacesof the cell from defects possibly introduced by the further handingassociated with final interconnections.

The lamination process 92 of FIG. 21 normally involves application ofheat and pressure. Temperatures of up to 600 degree F. are envisioned.Lamination temperatures of less than 600 degree F. would be more thansufficient to melt and activate not only typical polymeric sealingmaterials but also many low melting point metals, alloys and metallicsolders. For example, tin melts at about 450 degree F. and its alloyseven lower. Tin alloys with for example bismuth, lead and indium arecommon industrial materials. Many conductive “hot melt” adhesives can beactivated at even lower temperatures such as 300 degree F. Typicalthermal curing temperatures for polymers are in the range 200 to 350degree F. Thus, typical lamination practice widespread in the packagingindustry is normally appropriate to simultaneously accomplish manyconductive joining possibilities.

The sectional drawings of FIGS. 24 and 25 show the result of joiningmultiple articles 112 a, 112 b. Each article has a readily accessibledownward facing conductive surface pattern (in the drawing perspective)114 in communication with the cell top surface 59. A readily accessibleupward facing conductive surface pattern 116 extends from the cellbottom surfaces 66. It is clear that each unit 112 a, 112 b, etc. hasits own individual current collector structure 110 a harvesting currentfrom the cells top surface. Thus each cell is covered by its ownindividual substrate layer 70 a which is separate and distinct from thesubstrate layer of an adjacent cell.

One clearly recognizes that these readily accessible surfaces 114 and116 may function as terminal bars for the end cells of a modular arrayof interconnected cells. One also appreciates that as shown in thisembodiment, current collector 110 b functions as an interconnectingsubstrate unit. Series connections between adjacent cells are easilyachieved by overlapping the top surface extension 114 of one article 112b and a bottom surface extension 116 of a second article 112 a andelectrically connecting these extensions with electrically conductivejoining means such as conductive adhesive 42 shown in FIGS. 24 and 25.Other electrically conductive joining means including those definedabove may be selected in place of conductive adhesive 42. For example,surfaces 114 and 116 could overlap and be electrically joined to top andbottom surfaces of a metal foil member. Finally, since the articles 112of FIG. 23 can be produced in a continuous form (in the direction normalto the paper in FIG. 23) the series connections and array productionembodied in FIGS. 24 and 25 may also be accomplished in a continuousmanner by using continuous feed rolls of “tabbed cell stock” 112.However, while continuous assembly may be possible, other processing maybe envisioned to produce the interconnection embodied in FIGS. 24 and25. For example, defined lengths of “tabbed cell stock” 112 could beproduced by subdividing a continuous strip of “tabbed cell stock” 112 inthe Y dimension and the individual articles thereby produced could bearranged as shown in FIGS. 24 and 25 using, for example, standard pickand place positioning.

FIG. 26 is a top plan view of an article in production of anotherembodiment of a laminating current collector grid or electrode accordingto the instant invention. FIG. 26 embodies a polymer based film or glasssubstrate 120. Substrate 120 has width X-120 and length Y120. Inembodiments, taught in detail below, Y-120 may be much greater thanwidth X-120, whereby film 120 can generally be described as “continuous”in length and able to be processed in length direction Y-120 in acontinuous roll-to-roll fashion. FIG. 27 is a sectional view takensubstantially from the view 27-27 of FIG. 26. Thickness dimension Z-120is small in comparison to dimensions Y-120, X-120 and thus substrate 120may have a flexible sheetlike, or web structure contributing to possibleroll-to-roll processing. As shown in FIG. 27, substrate 120 may be alaminate of multiple layers 72 b, 74 b, 76 b etc. or may comprise asingle layer of material. Thus substrate 120 may have structure similarto that of the FIGS. 6 through 8 embodiment, and the discussion of thecharacteristics of article 70 of FIGS. 6 through 8 is proper tocharacterize article 120 as well. As with the representation of thearticle 70 of FIGS. 6 through 8, and as shown in FIG. 28, article 120(possibly multilayered) will be embodied as a single layer in thefollowing for simplicity of presentation.

FIG. 29 is a top plan view of an article 124 following an additionalprocessing step using article 120. FIG. 30 is a sectional viewsubstantially from the perspective of lines 30-30 of FIG. 29. Thestructure depicted in FIGS. 29 and 30 is similar to that embodied inFIGS. 16 and 18. It is seen that article 124 comprises a pattern of“fingers” or “traces”, designated 84 b, extending from “buss” or “tab”structures, designated 86 b. In the embodiments of FIGS. 29 and 30, both“fingers” 84 b and “busses” 86 b are positioned on supporting substrate120 in a grid pattern. “Fingers” 84 b extend in the width X-124direction of article 124 and “busses” (“tabs”) extend in the Y-124direction substantially perpendicular to the “fingers”. In the FIG. 29embodiment, it is seen that the distal ends 85 of the fingers locatedaway from the “buss” 86 b are joined by connecting trace of material 128extending in the “Y-124” direction. One readily understands that shouldan individual “finger’ 84 b become severed or otherwise conductivelyimpaired at a point along its length, the connecting material trace 128allows a shuttling of the affected current flow to an adjacent finger.In this way a defective finger does not appreciably detract from overallcell performance. One may also appreciate the substantial functionalredundancy characteristic of the grid/interconnect structures of theinvention.

In the embodiment of FIGS. 29 and 30, the buss 86 b region ischaracterized as having multiple regions 126 devoid of material forming“buss” 86 b. In the FIG. 29 embodiment, the voided regions 126 arepresented as circular regions periodically spaced in the “Y-124”direction. One will understand in light of the teachings to follow thatthe circular forms 126 depicted in FIG. 29 is but one of many differentpatterns possible for the voided regions 126. The sectional view of FIG.30 shows the voided regions 126 leave regions of the surface 80 b ofsubstrate 120 exposed. Surface 80 b of substrate 120 remains exposed inthose regions not covered by the finger/buss pattern. These exposedregions are further indicated by the numeral 127 in FIG. 29.

Structure 124 may be produced, processed and extend continuously in thelength “Y-124” direction.

Portions of substrate 120 not overlayed by material forming “fingers” 84b and “busses” 86 b remain transparent or translucent to visible light.These regions are generally identified by numeral 127 in FIG. 29. In theembodiment of FIGS. 29 and 30, the “fingers” 84 b and “busses” 86 b areshown to be a single layer for simplicity of presentation. However, the“fingers” and “busses” can comprise multiple layers of differingmaterials chosen to support various functional attributes. For examplethe material defining the “buss” or “finger” patterns which is in directcontact with substrate 120 may be chosen for its adhesive affinity tosurface 80 b of substrate 120 and also to a subsequently appliedconstituent of the buss or finger structure. Further, it may beadvantageous to have the first visible material component of the fingersand busses be of dark color or black. As will be shown, the lightincident side (outside surface) of the substrate 120 will eventually besurface 82. By having the first visible component of the fingers andbusses be dark, they will aesthetically blend with the generally darkcolor of the photovoltaic cell. This eliminates the often objectionableappearance of a metal colored grid pattern. Permissible dimensions andstructure for the “fingers” and “busses” will vary somewhat depending onmaterials and fabrication process used for the fingers and busses, andthe dimensions of the individual cell.

“Fingers” 84 b and “busses” 86 b may comprise electrically conductivematerial. Examples of such materials are metal wires and foils, stampedmetal patterns, conductive metal containing inks and pastes such asthose having a conductive filler comprising silver or stainless steel,patterned deposited metals such as etched metal patterns or maskedvacuum deposited metals, intrinsically conductive polymers and DERformulations. In a preferred embodiment, the “fingers and “busses”comprise electroplateable material such as DER or an electricallyconductive ink which will enhance or allow subsequent metalelectrodeposition. “Fingers” 84 b and “busses” 86 b may also comprisenon-conductive material which would assist accomplishing a subsequentdeposition of conductive material in the pattern defined by the“fingers” and “busses”. For example, “fingers” 84 b or “busses” 86 bcould comprise a polymer which may be seeded to catalyze chemicaldeposition of a metal in a subsequent step. An example of such amaterial is seeded ABS. Patterns comprising electroplateable materialsor materials facilitating subsequent electrodeposition are oftenreferred to as “seed” patterns or layers. “Fingers” 84 b and “busses” 86b may also comprise materials selected to promote adhesion of asubsequently applied conductive material. “Fingers” 84 b and “busses” 86b may differ in actual composition and be applied separately. Forexample, “fingers” 84 b may comprise a conductive ink while “buss/tab”86 b may comprise a conductive metal foil strip. Alternatively, fingersand busses may comprise a continuous unvarying monolithic materialstructure forming portions of both fingers and busses. Fingers andbusses need not both be present in certain embodiments of the invention.

The embodiments of FIGS. 29 and 30 show the “fingers” 84 b, “busses” 86b, and connecting trace 128 as essentially planar rectangularstructures. Other geometrical forms are clearly possible, especiallywhen design flexibility is associated with the process used to establishthe material pattern of “fingers” and “busses”. “Design flexible”processing includes printing of conductive inks or “seed” layers, foiletching or stamping, masked deposition using paint or vacuum deposition,and the like. For example, these conductive paths can have triangulartype surface structures increasing in width (and thus cross section) inthe direction of current flow. Thus the resistance decreases as netcurrent accumulates to reduce power losses. Alternatively, one mayselect more intricate patterns, such as a “watershed” pattern asdescribed in U.S. Patent Application Publication 2006/0157103 A1 whichis hereby incorporated in its entirety by reference. Various structuralfeatures, such as radiused connections between fingers and busses may beemployed to improve structural robustness.

It is important to note however that the laminating current collectorstructures of the instant invention may be manufactured utilizingcontinuous, bulk roll to roll processing. While the collector gridembodiments of the current invention may advantageously be producedusing continuous processing, one will recognize that combining of gridsor electrodes so produced with mating conductive surfaces may beaccomplished using either continuous or batch processing. In one case itmay be desired to produce photovoltaic cells having discrete defineddimensions. For example, single crystal silicon cells are often producedhaving X-Y dimensions of 6 inches by 6 inches. In this case thecollector grids of the instant invention, which may be producedcontinuously, may then be subdivided to dimensions appropriate forcombining with such cells. In other cases, such as production of manythin film photovoltaic structures, a continuous roll-to-roll productionof an expansive surface article can be accomplished in the “Y” directionas identified in FIG. 1. Such a continuous expansive photovoltaicstructure may be combined with a continuous arrangement of collectorgrids of the instant invention in a semicontinuous or continuous manner.Alternatively the expansive semiconductor structure may be subdividedinto continuous strips of cell stock. In this case, combining acontinuous strip of cell stock with a continuous strip of collector gridof the instant invention may be accomplished in a continuous orsemi-continuous manner.

FIG. 31 corresponds to the view of FIG. 30 following an additionaloptional processing step. The FIG. 31 article is now designated bynumeral 125 to reflect this additional processing. FIG. 31 showsadditional conductive material deposited onto the “fingers” 84 b and“buss” 86 b. In this embodiment additional conductive material isdesignated by one or more layers (88 b, 90 b) and the fingers and bussesproject above surface 80 b as shown by dimension “H”. It is understoodthat conductive material could comprise more than two layers or be asingle layer. Conductive material (88 b,90 b) is shown as a single layerin the FIG. 31 embodiment for ease of presentation. Article 125 isanother embodiment of a unit of “current collector stock”. Dimension “H”may be smaller than about 50 micrometers and thus the structure offingers and busses depicted in FIG. 31 may be considered as a “lowprofile” structure. In some cases it may be desirable to reduce theheight of projection “H” prior to eventual combination with a conductivesurface such as 59 or 66 of photovoltaic cell 10. This reduction may beaccomplished by passing the structures as depicted in FIGS. 30,31through a pressurized and/or heated roller or the like to embed“fingers” 84 b and/or “busses” 86 b into layer 72 b of substrate 120.

While each additional conductive material is shown the FIG. 31embodiment as having the same continuous monolithic material extendingover both the buss and finger patterns, one will realize that selectivedeposition techniques would allow the additional “finger” layers todiffer from additional “buss” layers. For example, as shown in FIG. 31,“fingers” 84 b have free surface 98 b and “busses” 86 b have freesurface 100 b. As noted, selective deposition techniques such as brushelectroplating or masked deposition would allow different materials tobe considered for the “buss” surface 100 b and “finger” surface 98 b. Ina preferred embodiment, at least one of the additional layers (88 b, 90b) etc. are deposited by electrodeposition, taking advantage of thedeposition speed, compositional choice, low cost and selectivity of theelectrodeposition process. Many various metals, including highlyconductive silver, copper and gold, nickel, tin and alloys can bereadily electrodeposited. In these embodiments, it may be advantageousto utilize electrodeposition technology giving an electrodeposit of lowtensile stress to prevent curling and promote flatness of the metaldeposits. In particular, use of nickel deposited from a nickel sulfamatebath, nickel deposited from a bath containing stress reducing additivessuch as brighteners, or copper from a standard acid copper bath havebeen found particularly suitable. Electrodeposition also permits precisecontrol of thickness and composition to permit optimization of otherrequirements of the overall manufacturing process for interconnectedarrays. Alternatively, these additional conductive layers may bedeposited by selective chemical deposition or registered masked vapordeposition. These additional layers (88, 90) may also compriseconductive inks applied by registered printing.

It has been found very advantageous to form surface 98 b of “fingers” 84b or surface 100 b of “busses” 86 b with a material compatible with theconductive surface with which eventual contact is made. In preferredembodiments, electroless deposition or electrodeposition is used to forma suitable metallic surface. Specifically electrodeposition offers awide choice of potentially suitable materials to form the surface.Corrosion resistant materials such as nickel, chromium, tin, indium,silver, gold and platinum are readily electrodeposited. When compatible,of course, surfaces comprising metals such as copper or zinc or alloysof copper or zinc may be considered. Alternatively, the surface 98 b maycomprise a conversion coating, such as a chromate coating, of a materialsuch as copper or zinc. Further, as will be discussed below, it may behighly advantageous to choose a material to form surfaces 98 b or 100 bwhich exhibits adhesive or bonding ability to a subsequently positionedabutting conductive surface. For example, it may be advantageous to formsurfaces 98 b and 100 b using an electrically conductive adhesive.Alternatively, it may be advantageous to form surface 100 b of “busses”86 b with a conductive material such as a low melting point alloy solderin order to facilitate electrical joining to a complimentary conductivesurface having electrical communication with an electrode of an adjacentphotovoltaic cell. For example, forming surfaces 98 b and 100 b withmaterials such as tin or alloys of tin with an alloying element such aslead, bismuth or indium would result in a low melting point surface tofacilitate electrical joining during subsequent lamination steps. Onewill note that materials forming “fingers” surface 98 b and “buss”surface 100 b need not be the same.

FIG. 32 depicts an arrangement of 3 articles just prior to a laminatingprocess according to a process embodiment such as that of FIG. 21. Inthe FIG. 32 embodiment, “current collector stock” 125 is positionedabove a photovoltaic cell 10. A second article of laminating “currentcollector stock”, identified by numeral 129, is positioned beneath cell10. Article 129 may be similar in structure to article 110 of FIG. 20.

FIG. 33 shows the article 130 resulting from passing the FIG. 32arrangement through a lamination process as depicted in FIG. 21. Thelamination process has applied article 125 to the top surface 59 of cell10. Thus, the conductive surface 98 b of grid “fingers” 84 b of article125 are fixed by the lamination in intimate contact with conductive topsurface 59 of cell 10. The grid pattern of “fingers” or traces 84 bextends over a preponderance of the light incident surface 59 of cell10. The lamination process has similarly positioned the conductivesurface 98 a of “fingers” 84 a of article 129 in intimate contact withthe bottom surface 66 of cell 10. The conductive material associatedwith current collector stock 125 extends past a first terminal edge 46of cell 10. The conductive material associated with current collectorstock 129 extends past second terminal edge 45 of cell 10. Theseextensions, identified by numerals 134 and 136 in FIG. 33, formconvenient “tab” surfaces to facilitate electrical connections to andfrom the actual cell. Thus article 130 can be properly characterized asa form or embodiment of a “tabbed cell stock”. One also realizes thatthese extensions 134, 136 also may function as “terminal bars” shouldthe cell occur as an end cell in an interconnected array.

In the present specification lamination has been shown as a means ofcombining the collector grid or electrode structures with a conductivesurface. However, one will recognize that other application methods tocombine the grid or electrode with a conductive surface may beappropriate such as transfer application processing. For example, in theembodiments such as those of FIG. 23 or 33, the substrate is shown toremain in its entirety as a component of the “tabbed cell stock” andfinal interconnected array. However, this is not a requirement. In otherembodiments, all or a portion of substrate may be removed prior to orafter a laminating process accomplishing positioning and attachment of“fingers” 84 and “busses” 86 to a conductive cell surface. In this case,a suitable release material (not shown) may be used to facilitateseparation of the conductive collector electrode structure from aremoved portion of substrate 70 during or following an application suchas the lamination process depicted in FIG. 21. Thus, in this case theremoved portion of substrate 70 would serve as a surrogate or temporarysupport to initially manufacture and transfer the grid or electrodestructure to the desired conductive surface. One example would be thatsituation where layer 72 of FIG. 7 would remain with the finalinterconnected array while layers 74 and/or 76 would be removed.

FIG. 34 embodies the combination of multiple portions of “tabbed cellstock” 130. In the FIG. 34 embodiment, an extension 134 a associatedwith a first unit of “tabbed cell stock” 130 a overlaps extension 136 bof an adjacent unit of “tabbed cell stock” 130 b. The same spatialarrangement exists between “tabbed cell stock” units 130 b and 130 c.The conductive surfaces associated with the mating extensions arepositioned and held in secure contact as a result of an adhesivematerial forming surface 80 b of the substrate 120 melting and fillingthe voided regions 126 as shown. The mating contact is additionallysecured by adhesive bonding produced by additional originally exposedregions of substrates. These originally exposed regions of substratesurface in the region of the mechanical and pressure induced electricaljoining between adjacent units of “tabbed cell stock” are identified bythe numeral 127 in the FIG. 34. It is clear that in the FIG. 34embodiment a secure and robust series electrical connection is achievedbetween adjacent units of “tabbed cell stock” by virtue of thelamination process taught herein.

Referring now to FIGS. 35 through 38, there are shown embodiments of astarting structure for another grid/interconnect article of theinvention. FIG. 35 is a top plan view of an article 198. Article 198comprises a polymeric film or glass sheet substrate generally identifiedby numeral 200. Substrate 200 has width X-200 and length Y-200. LengthY-200 is sometimes much greater the width X-200 such that film 200 canbe processed in essentially a “roll-to-roll” fashion. However, this isnot necessarily the case. Dimension “Y” can be chosen according to theapplication and process envisioned. FIG. 36 is a sectional view takensubstantially from the perspective of lines 36-36 of FIG. 35. Thicknessdimension Z-200 is normally small in comparison to dimensions Y-200 andX-200 and thus substrate 200 has a sheetlike structure and is oftenflexible. In the embodiment of FIG. 35, substrate 200 is furthercharacterized by having regions of essentially solid structure (Wc)combined with regions (Wi) having holes 202 extending through thethickness Z-200. In the FIG. 35 embodiment, the substantially solidregion is generally defined by a width Wc, representing a currentcollection region. The region with through-holes (holey region) isgenerally defined by width Wi, representing an interconnection region.Line 201, which may be imaginary, separates the two regions. Holes 202may be formed by simple punching, laser drilling and the like.Alternatively, holey region Wi may comprise a fabric joined to region Wcalong line 201, whereby the fabric structure comprises through-holes.The reason for these distinctions and definitions will become clear inlight of the following teachings.

Referring now to FIG. 36, region Wc of substrate 200 has a first surface210 and second surface 212. The sectional view of substrate 200 shown inFIG. 36 shows a single layer structure. This depiction is suitable forsimplicity and clarity of presentation. Often, however, film 200 willcomprise a laminate of multiple layers as depicted in FIG. 37. In theFIG. 37 embodiment, substrate 200 is seen to comprise multiple layers204, 206, 208, etc. As previously taught herein, for example in thediscussion of FIG. 7, the multiple layers may comprise inorganic ororganic components such as thermoplastics, thermosets, or siliconcontaining glass-like layers. The various layers are intended to supplyfunctional attributes such as environmental barrier protection oradhesive characteristics. In particular, in light of the teachings tofollow, one will recognize that it may be advantageous to have layer 204forming surface 210 comprise an adhesive sealing material such asethylene vinyl acetate (EVA), an ionomer, an olefin based adhesive,atactic polyolefin, or a polymer containing polar functional groups foradhesive characteristics during a possible subsequent laminationprocess. For example, the invention has been successfully demonstratedusing a standard laminating material sold by GBC Corp., Northbrook,Ill., 60062. Additional layers 206, 208 etc. may comprise materialswhich assist in support or processing such as polypropylene,polyethylene terepthalate and polyethylene naphthalate (PEN), barriermaterials such as fluorinated polymers, biaxially oriented polypropylene(BOPP), poly(vinylidene chloride), such as Saran, a product of DowChemical, and Siox, and materials offering protection againstultraviolet radiation as previously taught in characterizing substrate70 of FIG. 6.

As embodied in FIGS. 35 and 36, the solid regions Wc and “holey” regionsWi of substrate 200 may comprise the same material. This is notnecessarily the case. For example, the “holey” regions Wi of substrate200 could comprise a fabric, woven or non-woven, joined to an adjacentsubstantially solid region along line 201. However, the materialsforming the solid region Wc should be relatively transparent ortranslucent to visible light, as will be understood in light of theteachings to follow.

An alternate structure is embodied in FIGS. 35A and 36A. There astructure 199 is formed by seaming two sheetlike material forms 213 and215. Structure 199 itself has an overall sheetlike form havingoppositely facing surfaces 210 a and 212 a. Material form 213 istransparent or translucent. Material form 215 is electricallyconductive. Material form 215 may comprise materials such as anelectrically conductive polymer, a bulk metal foil or a fabriccomprising metal fibrils. It is important to note that the sheetlikestructure 199 has electrical conductivity through its thickness Z-199from surface 210 a to surface 212 a in the region Wi. While shown assingle layers, it is understood that material forms 213 and 215 maycomprise multiple distinct layers.

FIG. 38 depicts an embodiment wherein multiple widths 200-1, 200-2 etc.of the general structure of FIGS. 35 and 36 are joined together in agenerally repetitive pattern in the width direction. Such a structureallows simultaneous production of multiple repeat structurescorresponding to widths 200-1, 200-2 in a fashion similar to that taughtin conjunction with the embodiments of FIGS. 6 through 15.

FIG. 39 is a plan view of the FIG. 35 substrate 200 following anadditional processing step, and FIG. 40 is a sectional view taken alongline 40-40 of FIG. 39. In FIGS. 39 and 40, the article is now designatedby the numeral 214 to reflect this additional processing. In FIGS. 39and 40, it is seen that a pattern of “fingers” or traces 216 has beenformed by material 218 positioned in a pattern onto surface 210 oforiginal sheetlike substrate 200. “Fingers” or traces 216 extend overthe width Wc of the solid portion of sheetlike structure 214. The“fingers” 216 extend to the “holey” interconnection region generallydefined by Wi. Portions of the Wc region not overlayed by “fingers” 216remain transparent or translucent to visible light. The “fingers” maycomprise electrically conductive material. Examples of such materialsare metal containing inks, patterned deposited metals such as etchedmetal patterns, stamped metal patterns, masked vacuum deposited metalpatterns, fine wires, intrinsically conductive polymers and DERformulations. In other embodiments the “fingers” may comprise materialsintended to facilitate subsequent deposition of conductive material inthe pattern defined by the fingers. An example of such a material wouldbe ABS, catalyzed to constitute a “seed” layer to initiate chemical“electroless” metal deposition. Another example would be a materialfunctioning to promote adhesion of a subsequently applied conductivematerial to the film 200. In a preferred embodiment, the “fingers”comprise material which will enhance or allow subsequent metalelectrodeposition such as a DER or electrically conductive ink. In theembodiment of FIGS. 39 and 40, the “fingers” 216 are shown to be asingle layer of material 218 for simplicity of presentation. However,the “fingers” can comprise multiple layers of differing materials chosento support various functional attributes as has previously been taught.

Continuing reference to FIGS. 39 and 40 also shows additional material220 applied to the “holey” region Wi of article 214. As with thematerial comprising the “fingers” 216, the material 220 applied to theregion Wi is either conductive or material intended to facilitatesubsequent deposition of conductive material.

In an alternate embodiment, region Wi may comprise a fabric which mayfurther comprise conductive material extending through the natural holesof the fabric. Further, such a fabric may comprise fibrils formed fromconductive materials such as metals or conductive polymers. Theconductive fibrils can be intermixed with nonconductive fibrils to givea fabric combining metallic characteristics such as high conductivitywith polymer characteristics such as flexibility and adhesive affinityto a mating conductive surface such as the bottom surface of aphotovoltaic cell. Moreover, a fabric structure can be expected toincrease and retain flexibility after subsequent processing such asmetal electroplating and perhaps bonding ability of the ultimateinterconnected cells as will be understood in light of the teachingscontained hereafter.

In the embodiment of FIGS. 39 and 40, the “holey” region takes thegeneral form of a “buss” 221 extending in the Y-214 direction incommunication with the individual fingers. However, as one willunderstand through the subsequent teachings, the invention requires onlythat conductive communication extend from the fingers to a region Wiintended to be electrically joined to the bottom conductive surface ofan adjacent cell. The region Wi thus does not require overall electricalcontinuity in the “Y” direction as is characteristic of a “buss” formdepicted in FIGS. 39 and 40.

Reference to FIG. 40 shows that the material 220 applied to the “holey”interconnection region Wi is shown as the same as that applied to formthe fingers 216. However, these materials 218 and 220 need not beidentical. It is understood that while the material extending oversurface 212 is shown in the figure to mirror structure on surface 210this need not be the case. The pattern of material positioned on surface212 may differ from that on surface 210 in dimensional structure and/orcomposition. In this embodiment material 220 applied to the “holey”region extends through holes 202 and onto the opposite second surface212 of article 214. The extension of material 220 through the holes 202can be readily accomplished as a result of the relatively smallthickness (Z dimension) of the sheetlike substrate 200. Techniquesinclude two sided printing of material 220, through hole sprayapplication, masked metallization or selective chemical deposition ormechanical means such as stapling, wire sewing or riveting.

FIG. 41 is a view similar to that of FIG. 40 following an additionaloptional processing step. The article embodied in FIG. 41 is designatedby numeral 226 to reflect this additional processing. It is seen in FIG.41 that the additional processing has deposited highly conductivematerial 222 over the originally free surfaces of materials 218 and 220.Material 222 normally comprises metal-based material such as copper ornickel, tin or a conductive metal containing paste or ink. Typicaldeposition techniques such as printing, chemical or electrochemicalmetal deposition and masked deposition can be used for this additionaloptional process to produce the article 226. In a preferred embodiment,electrodeposition is chosen for its speed, ease, and cost effectivenessas taught above. It is understood that articles 214 and 226 areembodiments of “current collector stock”.

It is seen in FIG. 41 that highly conductive material 222 extendsthrough holes to electrically join and form electrically conductivesurfaces on opposite sides of article 226. It is understood that whilethe conductive material extending over surface 212 of region Wi is shownin the Figures to mirror structure on surface 210 this need not be thecase. The pattern of conductive material positioned on surface 212 maydiffer from that on surface 210 in dimensional, structural and/orcompositional pattern. While shown as a single layer in the FIG. 41embodiment, the highly conductive material can comprise multiple layersto achieve functional value. In particular, a layer of copper is oftendesirable for its high conductivity. Nickel is often desired for itsadhesion characteristics, plateability and corrosion resistance. Theexposed surface 229 of material 222 can be selected for corrosionresistance and bonding ability. It has been found very advantageous toform surface 229 with a material compatible with the conductive surfacewith which eventual contact is made. In preferred embodiments,electroless deposition or electrodeposition is used to form a suitablemetallic surface. Specifically electrodeposition offers a wide choice ofpotentially suitable materials to form the surface 229. Corrosionresistant materials such as nickel, chromium, tin, indium, silver, goldand platinum are readily electrodeposited may be chosen to form surface229. When compatible, of course, surfaces comprising metals such ascopper or zinc or alloys of copper or zinc may be considered.Alternatively, the surface 229 may comprise a conversion coating, suchas a chromate coating, of a material such as copper or zinc. Further, itmay be highly advantageous to choose a material, such as a conductiveadhesive or metallic solder to form surface 229 which exhibits adhesiveor bonding ability to a subsequently positioned abutting conductivesurface. In this regard, electrodeposition offers a wide choice ofmaterials to form surface 229. In particular, indium, tin or tincontaining alloys are a possible choice of material to form the exposedsurface 229 of material 222. These metals melt at relatively lowtemperatures less than about 500 degree Fahrenheit. Thus these metalsmay be desirable to promote ohmic joining, through soldering, to othercomponents in subsequent processing such as lamination. Alternatively,exposed surface 229 may comprise an electrically conductive adhesive.Selective deposition techniques such as brush plating or printing wouldallow the conductive materials of region Wi to differ from those offingers 216. In addition to supplying electrical communication fromsurfaces 210 to 212, holes 202 also function to increase flexibility of“buss” 221 by relieving the “sandwiching” effect of continuousoppositely disposed layers. Holes 202 can clearly be the holes naturallypresent should substrate 200 in the region Wi be a fabric.

One appreciates that in the embodiments of FIGS. 39 through 41electrical communication between oppositely facing surface regions 210and 212 is achieved using holes 202 which constitute vias for conductivematerial extending between oppositely facing surface regions 210 and 212of articles 214/226. The holes shown in the embodiments are but one of anumber of different ways to achieve such communication. One alternatemeans of establishing such electrical communication was embodied inFIGS. 35A and 36A. There material 215 of region Wi of sheetlike article199 comprised an electrically conductive material extending betweensurfaces 210 a and 212 a. Material form 215 may comprise materials suchas an electrically conductive polymer, a bulk metal foil or a fabriccomprising metal fibrils.

FIG. 41A is a sectional view of the FIGS. 35A/36A embodiment followingan additional processing step depositing conductive material 222 a ontothe surface 210 a. The FIG. 41A embodiment is identified as 226 a toreflect this additional processing. Material 222 a forms conductivetraces or fingers 216 a extending across surface 210 a and overlapping aportion of material 215 in the region Wi. Electrical communication maythereby be achieved between the “fingers”, the conductive material 215of region Wi and consequently that portion of surface 212 a withinregion Wi. Thus in this embodiment the conductive material 215 issubstituted for the conductive material 222 extending through the holes202 of FIG. 41.

While shown as a single layer, finger 216 a may comprise multiplematerials and layers as has previously been discussed for the materialtraces of FIGS. 39 through 41. Moreover one may formulate material 215to comprise an electrically conductive polymer having an adhesiveaffinity to the bottom surface of a photovoltaic cell. Such an adhesiveaffinity could be conveniently activated by heat and/or pressureassociated with a laminating process to electrically and physically joina conductive portion of surface 212 a to the bottom surface 66 of aphotovoltaic cell.

One method of combining the current collector stock 226 embodied in FIG.41 with a cell stock 10 as embodied in FIGS. 1A and 2A is illustrated inFIGS. 42 and 43. In the FIG. 43 structure, individual current collectorstocks 226 are combined with cells 10 a, 10 b, 10 c respectively toproduce a series interconnected array. This may be accomplished via aprocess generally described as follows.

As embodied in FIG. 42, a unit of “current collector stock”, such as226, is combined with a cell such as 10 by positioning of surface region“We” of current collector stock 226 having free surface 210 inregistration with the light incident surface 59 of cell 10. The gridpattern of “fingers” or traces 216 extends over a preponderance of thelight incident surface 59 of cell 10. The article so produced,identified as 227, is another embodiment of “tabbed cell stock”.Adhesion joining the two surfaces is accomplished by a suitable process.In particular, the material forming the remaining free surface 210 ofarticle 226 (that portion of surface 210 not covered with conductivematerial 222) may be a sealing material chosen for adhesive affinity tosurface 59 of cell 10 thereby promoting good adhesion between thecollector stock 226 and cell surface 59 resulting from a laminatingprocess such as that depicted in FIG. 21. Such a laminating processbrings the conductive material of fingers 216 into firm and effectivecontact with the window electrode 18 forming surface 59 of cell 10. Thiscontact is ensured by the blanketing “hold down” afforded by theadhesive bonding adjacent the conductive fingers 216. One skilled in theart will further understand that the nature of the polymer support layersuch as may be represented by layer 206 of FIG. 37, may be important inensuring the integrity of the blanket “hold down”. This is because themechanical properties such as tensile modulus of the support layer willoften exceed that of the adhesive bonding layer. Therefore, the“blanket” is less susceptible to movement over time when exposed toenvironmental conditions such as thermal cycling. Also, as mentionedabove, the nature of the free surface of conductive material 222 mayoptionally be manipulated and chosen to further enhance ohmic joiningand adhesion.

Both batch or continuous laminating are suitable when combining a unitof “current collector stock” with a cell 10 to produce the “tabbed cellstock” 227. The invention has been demonstrated using both rolllaminators and batch vacuum laminators. Should the articles 226 and 10be in a continuous form it will be understood that the combinationarticle 227 could be formed continuously and possibly collected as acontinuous “tabbed cell stock”.

Referring to FIG. 43, it is seen that proper positioning allows theconductive material 222 extending over the second surface 212 of article227 b to be ohmicly adhered to the bottom surface 66 of cell 10 a. Thisjoining is accomplished by suitable electrical joining techniques suchas soldering, riveting, spot welding or conductive adhesive application.The particular ohmic joining technique embodied in FIG. 43 is throughelectrically conductive adhesive 42. A particularly suitable conductiveadhesive is one comprising a carbon black filler in a polymer matrixpossibly augmented with a more highly conductive metal filler. Suchadhesive formulations are relatively inexpensive and can be produced ashot melt formulations. Despite the fact that adhesive formulationsemploying carbon black alone have relatively high intrinsicresistivities (of the order 1 ohm-cm.), the bonding in this embodimentis accomplished through a relatively thin adhesive layer and over abroad surface. Thus the resulting resistance losses are relativelylimited. A hot melt conductive adhesive is very suitable forestablishing the ohmic connection using a straightforward laminationprocess. A hot melt conductive adhesive melts during the laminationprocess and firmly joins the conductive surfaces upon cooling.

FIG. 43 embodies multiple cells assembled in a series arrangement usingthe teachings of the instant invention. In FIG. 43, “i” indicates thedirection of net current flow and “hv” indicates the light incidence forthe arrangement. It is noted that the arrangement of FIG. 43 resembles ashingling arrangement of cells, but with an important distinction. Theprior art shingling arrangements have included an overlapping of cellsat a sacrifice of portions of very valuable cell surface. In the FIG. 43teaching, the benefits of the shingling interconnection concept areachieved without any loss of photovoltaic surface from shading by anoverlapping cell. In addition, the FIG. 43 arrangement retains a highdegree of flexibility because there is no immediate overlap of the metalfoil cell substrate.

Yet another form of the instant invention is embodied in FIGS. 44through 56. FIG. 44 is a top plan view of a substrate article designated230. Article 230 has width “X-230” and length “Y-230”. It iscontemplated that “Y-230” may be considerably greater than “X-230” suchthat article 230 may be processed in continuous roll-to-roll fashion.However, such continuous processing is not a requirement.

FIG. 45 is a sectional view taken substantially from the perspective oflines 45-45 of FIG. 44. It is shown in FIG. 45 that article 230 maycomprise any number of material layers such as those designated bynumerals 232, 234, 236. The layers are intended to supply functionalattributes to substrate article 230 as has been discussed for priorembodiments, for example in FIG. 7. Article 230 is also shown to havethickness “Z-230”. “Z-230” is much smaller than “X-230” or “Y-230” andthus article 230 can generally be characterized as being flexible andsheetlike. Article 230 is shown to have a first surface 238 and secondsurface 240. As will become clear in subsequent embodiments, it may beadvantageous to form layer 232 forming surface 238 using a materialhaving adhesive affinity to the bottom surface 66 of cell 10. Inaddition, it may be advantageous to have surface 240 formed by amaterial having adhesive affinity to surface 59 of cell 10. Thematerials forming surfaces 238 and 240 may be the same or be different.As has been previously described, layer 234 may comprise a structuralpolymer layer such as polypropylene, polyethylene terepthalate (PET),polyethylene naphthalate (PEN), acrylic or polycarbonate.

Many alternate embodiments for substrate articles exist. For example,FIG. 46 is an alternate sectional embodiment depicting a substratearticle 230 a. The layers forming article 230 a do not necessarily haveto extend over the entire expanse of article 230 a. In FIG. 46, only aportion of the upward facing surface 238 a of article 230 a is formed bymaterial layer 232 a. Another portion of surface 238 a is formed bymaterial layer 234 a. Similarly only a portion of the downward facingsurface 240 a is formed by material layer 236 a. Another portion of thedownward facing surface 240 a is formed by material layer 234 a. As willbe shown, material layer 236 a eventually is positioned to overlay thelight incident surface 59 of a photovoltaic cell and therefore istransparent or translucent. In addition, it may be advantageous tochoose material 236 a to have adhesive affinity to the top surface 59 ofa photovoltaic cell 10. Material 232 a is eventually positioned tocontact the bottom surface 66 of a photovoltaic cell 10. Thus, it may beadvantageous to choose material 232 a to have adhesive affinity to thebottom surface 66 of a photovoltaic cell 10. One also understands thatmaterial 232 a need not necessarily be transparent or translucent sinceit is overlayed by the cell. In some embodiments materials 232 a and 236a may be different or in other embodiments they may be the same.Furthermore, the thickness of materials 232 a and 236 a may differ.

In some embodiments the substrate articles “230” will comprise a commoninsulating carrier or support layer extending over the full width andlength of the article. See, for example, layer 234 a of FIG. 46. Such acommon layer is often present to facilitate handling and processing andto support the various functional layers associated with the article.However, it is noted that such a common layer is not necessary forpractice of the invention. Articles “230” comprising a patchwork ofdiffering sheetlike portions may be employed. Further, one willappreciate in light of the teachings to follow that articles “230” maycomprise multiple, discrete and separated sheetlike portions joined in away to maintain the spatial arrangement of the discrete portions.

An example of an alternate embodiment is depicted in FIG. 46A. FIG. 46Ais a sectional view showing a sheetlike substrate article 230 b havingan arrangement of joined portions. A first portion is characterized ashaving surface 240 b formed from a transparent or translucent material236 b having adhesive affinity for the top surface 59 of photovoltaiccell 10. A second portion has surface 238 b formed by a material 232 bhaving adhesive affinity to the bottom surface 66 of cell 10. Theindividual portions each may have an optional carrier or support layer(231/233) to facilitate processing and possibly support functionallayers. The carrier or support layers (231/233) are normally structuralpolymeric materials such as polypropylene, polyethylene terepthalate(PET), polyethylene naphthalate (PEN), acrylic or polycarbonate. After aseaming operation joins the portions together as shown, the overallarticle 230 b assumes a substantially planar sheetlike form. Seaming maybe accomplished by any number of known techniques such as laminatingoverlapping regions, stitching and adhesive bonding. A common feature ofsuch articles “230” is that they have a portion of upward facing surface“238” comprising a material having adhesive affinity for a bottomsurface of a photovoltaic cell and a portion of downward facing surface“240” comprising a material having adhesive affinity for a top lightincident surface of a photovoltaic cell.

Another embodiment of the substrate articles “230” is illustrated inFIGS. 46C and 46D. There an article 230 c is embodied which comprisesthree distinct portions patched together into a sheetlike form. A firstmaterial form 245 is transparent or translucent. Portions of surface 240formed by material form 245 have adhesive affinity for the upper surface59 of photovoltaic cells. Material form 246 forms a portion of surface238 having adhesive affinity for the bottom surfaced 66 of aphotovoltaic cell. Material forms 245 and 246 are positioned and joinedtogether using conductive material 215 a. Material 215 a may comprise aconductive polymer, a bulk metal foil, a metal mesh or fabric comprisingmetal fibrils and the like. Material 215 a supplies a conductivecommunication between surfaces 240 c and 238 c. While shown as singlelayers, it is understood that material forms 245, 215 a, and 246 maycomprise multiple materials and layers.

Another embodiment of the substrate articles “230” is depicted in FIG.46F. In this top plan view an embodiment comprising two sheetlikeportions 247 and 248 is shown in relative position. While not shown inFIG. 46F, portion 247 has a surface 240 d which has adhesive affinity toa top surface 59 of a photovoltaic cell. Portion 248 has an oppositelyfacing surface 238 d having adhesive affinity to the bottom surface 66of a photovoltaic cell.

FIG. 47 is a simplified sectional view of the substrate articles “230”which will be used to simplify presentation of teachings to follow.While FIG. 47 presents articles 230 as a single layer, it is emphasizedthat in the teachings to follow articles 230 may comprise any number oflayers and structural portions as taught above. One will readilyunderstand the application of the inventive concepts to follow whenusing the various article embodiments 230 through 230 d of the priorFigures. A common feature of all such articles “230” is that they havean upward facing surface 238 at least a portion of which is formed by amaterial having adhesive affinity for a bottom surface of a photovoltaiccell and a downward facing surface 240 at least a portion of which isformed by a material having adhesive affinity for a top light incidentsurface of a photovoltaic cell. The materials forming these adhesivesurfaces may be the same or different.

FIG. 48 is a top plan view of the initial article 230 following anadditional processing step. The article embodied in FIG. 48 isdesignated 244 to reflect this additional processing step. FIG. 49 is asectional view taken substantially from the perspective of lines 49-49of FIG. 48. Reference to FIGS. 48 and 49 show that the additionalprocessing has produced holes 242 in the direction of “Y-244”. The holesextend from the surface 238 to the surface 240 of article 244. Holes 242may be produced by any number of techniques such as laser drilling orsimple punching.

FIG. 50 is a top plan view of the article 244 following an additionalprocessing step. The article of FIG. 50 is designated 250 to reflectthis additional processing. FIG. 51 is a sectional view takensubstantially from the perspective of lines 51-51 of FIG. 50. Referenceto FIGS. 50 and 51 shows that material 251 has been applied to the firstsurface 238 in the form of “fingers” 252. Further, material 253 has beenapplied to second surface 240 in the form of “fingers” 254. In theembodiment, “fingers” 252 and 254 extend substantially perpendicularfrom a “buss-like” structure 256 extending in the direction “Y-250”. Asseen in FIG. 51, additional materials 251 and 253 extend through theholes 242. In the FIG. 51 embodiment, materials 251 and 253 are shown asbeing the same. This is not necessarily a requirement and they may bedifferent. Also, in the embodiment of FIGS. 50 and 51, the buss-likestructure 256 is shown as being formed by materials 251/253. This is notnecessarily a requirement. Materials forming the “fingers” 252 and 254and “buss” 256 may all be the same or they may differ in actualcomposition and be applied separately. Alternatively, fingers and bussesmay comprise a continuous material structure forming portions of bothfingers and busses. Fingers and busses need not both be present incertain embodiments of the invention.

As in prior embodiments, “fingers” 252 and 254 and “buss” 256 maycomprise electrically conductive material. Examples of such materialsare metal wires and metal foils, conductive metal containing inks andpastes, patterned metals such as etched or punched metal patterns ormasked vacuum deposited metals, intrinsically conductive polymers,conductive inks and DER formulations. In a preferred embodiment, the“fingers and “busses” comprise material such as DER or an electricallyconductive ink such as silver containing ink which will enhance or allowsubsequent metal electrodeposition. “Fingers” 252 and 254 and “buss” 256may also comprise non-conductive material which would assistaccomplishing a subsequent deposition of conductive material in thepattern defined by the “fingers” and “busses”. For example, “fingers”252 and 254 or “buss” 256 could comprise a polymer which may be seededto catalyze chemical deposition of a metal in a subsequent step. Anexample of such a material is ABS. “Fingers” 252 and 254 and “buss” 256may also comprise materials selected to promote adhesion of asubsequently applied conductive material.

FIG. 52 is a sectional view showing the unit article 250 following anadditional optional processing step. The article of FIG. 52 isdesignated 260 to reflect this additional processing. In a fashion likethat described above for production of prior embodiments of currentcollector structures, additional conductive material 266 has beendeposited by optional processing to produce the article 260 of FIG. 52.The discussion involving processing to produce the articles of FIGS.12-15, 20, 31, and 41 is proper to describe the additional processing toproduce the article 260 of FIG. 52. In a preferred embodiment,conductive material 266 may comprise material applied byelectrodeposition. In addition, while shown in FIG. 52 as a singlecontinuous, monolithic layer, the additional conductive material maycomprise multiple layers and materials. As in prior embodiments, it maybe advantageous to use a material such as a low melting point alloy orconductive adhesive to form exterior surface 268 of additionalconductive material 266. Additional conductive material overlaying“fingers” 252 need not be the same as the additional conductive materialoverlaying “fingers” 254.

One appreciates that in the embodiments of FIGS. 50 through 52electrical communication between conductive patterns on oppositelyfacing surfaces 238 and 240 is achieved using holes 242 which constitutevias for conductive material extending between oppositely facing surface238 and 240 of articles 250/260. The holes shown in the embodiments arebut one of a number of different ways to achieve such communication.

An alternate means of providing electrical communication betweenconductive patterns extending over oppositely facing surfaces of asheetlike substrate is depicted in FIG. 46B. In FIG. 46B, the article ofFIG. 46A is modified with additional structure. In FIG. 46B a metal formsuch as a wire 266 a extends over surface 238 b, through the substratewhere portions of the substrate overlap and further over surface 240 b.The metal wires or ribbons may be mechanically attached to therespective surfaces by partially embedding the wires or ribbons into thesurfaces. Vias for conductive material are the natural holes 242 aformed by the wire penetrating through the substrate.

FIG. 46E embodies an alternate arrangement. FIG. 46E shows additionalconductive structure 266 b extending over opposite faces of substrate230 c of FIG. 46C FIG. 46D. In FIG. 46E the article is identified as 260b to reflect this additional structure. As previously described,material 215 a in region Wi of sheetlike article 260 b comprises anelectrically conductive material extending between surfaces 240 c and238 c. Material form 215 a may comprise materials such as anelectrically conductive polymer, a bulk metal foil or a fabriccomprising metal fibrils. In the FIG. 46E embodiment, additionalconductive material 266 b forms conductive traces or fingers extendingover surfaces 240 c of material form 245 and surface 238 c of material246. The conductive traces on opposite surfaces of article 260 b overlapand contact material 215 a to thereby establish electrical communicationbetween the conductive trace patterns on opposite sides of the article260 b. Thus in this embodiment the conductive material 215 a issubstituted for the conductive material extending through the holes 242of FIG. 52. While shown as a single layer, material form 266 b maycomprise multiple materials and layers as has previously been discussedfor such traces.

FIGS. 46G and 46H embody a modification to the structure of FIG. 46F.The new modified structure is identified as 260 c. In the FIGS. 46G and46H, it is seen that portions 247 and 248 have been joined and fixed inrelative spatial position using metal wires or ribbons 266 c extendingbetween the two portions. In addition, the wires extend over a surface238 d of portion 248 and also surface 240 d of portion 247. Aspreviously indicated, surface 238 d of portion 248 would have adhesiveaffinity for a bottom surface of a photovoltaic cell and surface 240 dof portion 247 would have adhesive affinity to a top surface 59 of aphotovoltaic cell. The metal wires or ribbons could be mechanicallyattached to the respective surfaces by partially embedding the wires orribbons into the surfaces. This attachment may be enhanced by adhesivecharacteristics of the material forming the surface itself.Alternatively attachment of the wires to the surfaces by first coatingwith a conductive adhesive may be considered.

The alternate structural embodiments “260” of FIGS. 46B, 46E, 46H and 52may be characterized as “laminating current collector/interconnect”assemblies or as units of interconnecting structure. Inspection of theembodiments reveals some important common characteristics for such“laminating current collector/interconnect” assemblies:

-   -   at least a portion of the substrate is formed by a transparent        or translucent material.    -   the articles all have a portion of a downward facing surface        formed by a material having adhesive affinity for a top        conductive surface of a photovoltaic cell and further having an        electrically conductive pattern extending over that portion of        downward facing surface.    -   the articles all have a portion of an upward facing surface        which is formed by a material having adhesive affinity for a        bottom conductive surface of a photovoltaic cell and further        having an electrically conductive pattern extending over that        portion of upward facing surface.    -   the articles all have electrical communication between the        conductive patterns positioned on the upward facing and downward        facing surface portions.

In many cases the articles “260” will also comprise a multilayeredlaminating sheet comprising a structural plastic layer supporting anadhesive layer.

The sectional views of FIGS. 55 and 56 embody the use of articles 250 or260 to achieve a series connected structural array of photovoltaic cells10. In FIG. 55, an article designated as 270 has been formed bycombining article 260 with cell 10 by laminating the surface 240 ofarticle 260 to the top conductive surface 59 of cell 10. The gridpattern of “fingers” or traces 254 extends over a preponderance of thelight incident surface 59 of cell 10. In a preferred embodiment,portions of exposed surface 240 (regions not covered with “fingers” 254)are formed by a material having adhesive affinity to surface 59 and asecure and extensive adhesive bond forms between surfaces 240 and 59during the heat and pressure exposure of the lamination process. Thus anadhesive “blanket” holds conductive material 266 of “fingers” 254 insecure contact with surface 59. One skilled in the art will furtherunderstand that the nature of the polymer support layer such as may berepresented by layer 234 of FIG. 45 may be important in ensuring theintegrity of the blanket “hold down”. This is because the mechanicalproperties such as tensile modulus of the support layer will oftenexceed that of the adhesive bonding layer. Therefore, the “blanket” isless susceptible to movement over time when exposed to environmentalconditions such as thermal cycling. As previously pointed out, lowmelting point alloys or conductive adhesives may also be considered toenhance this contact although these measures have not been necessary toestablish excellent contact between cell surfaces and the laminatedtraces.

It is understood that article 270 of FIG. 55 is yet another embodimentof a “tabbed cell stock”. One clearly appreciates that the “tabbed cellstock” article 270 has readily accessible surfaces of opposite cellpolarity. Surface 66 is readily accessible as seen. Conductive material266 contacts top cell surface 59 and extends to form an accessiblesurface removed from the cell. Thus, the performance characteristics ofthe “tabbed cell” can be readily determined. This allows immediate andfacile identification of cell performance characteristics, sorting ofcell material according to performance and removal of defective cellmaterial.

An additional feature of the laminating “current collector/interconnect”assemblies 260 embodied in FIGS. 46B, 46E, 46H and 52 is the extendingportion comprising conductive material positioned on second surface 238.Choosing material forming surface 238 to have adhesive affinity to thebottom surface 66 of a photovoltaic cell allows electrical connection tobe achieved during lamination of surface 238 to bottom surface 66 ofcells 10. Accordingly, the sectional view of FIG. 56 embodies multiplearticles 270 arranged in a series interconnected array. The seriesconnected array is designated by numeral 290 in FIG. 56. In the FIG. 56embodiment, it is seen that “fingers” 252 positioned on surface 238 ofarticle 270 b have been brought into contact with the bottom surface 66of cell 10 associated with article 270 a. This contact is achieved bychoosing material 232 forming free surface 238 of article 270 b to haveadhesive affinity for bottom conductive surface 66 of cell 10 of article270 a. Secure adhesive bonding is achieved during the heat and pressureexposure of a laminating process thereby resulting in a hold down of the“fingers” 252 in contact with surface 66. In addition, it is clear thatthe extension of the unit of interconnect structure 260 to adjacentcells physically secures the cells in adjacent positioning.

It may be important to realize that contact between the conductivesurfaces of the article 260 and the photovoltaic cells is achieved viapressure exerted by the “blanketing effect” of adhesive layers ofarticle 260 contacting the corresponding photovoltaic cell surface. Itis important to understand that these contacts may be achieved withoutthe use of solders or conductive adhesives.

Thus, it is seen that with the FIG. 56 structure the current collectionand electrical communication may achieved with continuous, monolithicconductive structure extending between the top surface of one cell andthe bottom or rear surface of an adjacent cell. One readily appreciatesthat no solder or electrically conductive adhesives are required toachieve the current collection and interconnecting contacts associatedwith the FIG. 56 structure. This avoids potential degradation ofcontacts sometimes experienced when using conductive adhesives orsolders. One realizes that a similar elimination of a requirement forsolder or conductive adhesives is associated with many of the priorembodiments of the instant invention. However, as discussed above onemay choose to employ low melting point metals or conductive adhesives atthe contacting surfaces of the electrical traces if desirable.

In addition, the FIG. 56 embodiment clearly shows an advantageous“shingling” type structure that minimizes shielding of valuablephotovoltaic cell surface. As seen, the only light shielding of thephotovoltaic cells is from the traces 254. No overlapping of cells isrequired, as has been the case for “legacy” shingled arrangements.Furthermore, the FIG. 56 structural arrangement requires no separation,in a direction parallel to the cell surface, among adjacent cells. Thiscontrasts with legacy “string and tab” approaches which employ such aseparation for positioning of tabs and short prevention.

It is seen that the structural embodiment of FIG. 56 includes completeencapsulation of cells 10. This is achieved by having article 260 be ofsufficient width dimension to exceed the combined span of two adjacentcells. Surface 240 of a first article 270 extends slightly past aterminal edge of a first cell and surface 238 extends sufficiently tocomplete encapsulation of the cells as shown.

The sectional view of FIG. 56 suggests sharp and abrupt variations insurface topography when traversing right to left from cell-to-cell.These variations are a result of the drawing format only and do notrepresent actual surface variations of the article. Indeed, variationsin surface topography of actual articles are slight when considering thehorizontal distances over which they occur. This is a result of therelatively small thickness dimensions (dimension “Z” in the variousdrawing embodiments) characteristic of both the interconnectingsubstrate structure and the thin film photovoltaic cells taught herein.Indeed, the actual surface topography of the embodiments such as that ofFIG. 56 may in practice be characterized as substantially planar.

Smooth undulations in surface topography are important. First, effortsto overlay integrated modular cell arrays with flexible barrier filmsnormally demand a substantially planar surface upon which to laminatethe barrier film. The importance of surface planarization prior toapplication of barrier films is discussed in U.S. patent applicationSer. No. 12/372,720, the entire contents of which are herebyincorporated by this reference. It is readily appreciated that the upperand lower surfaces of the modular arrays as depicted in FIG. 56 areformed by smooth polymeric films forming a structure having very lowaspect ratio (depth to width ratio) and wherein the seams between theunits are smoothed by the pressures and material flow during thelamination step. Thus requirements for thick intermediary“planarization” layers between the modular arrays taught herein, such asthat of FIG. 56, and overlaying functional layers are avoided.Furthermore, material defects are avoided during a subsequent laminationof the flexible barrier film.

A second significant advantage of the structure embodied in FIG. 56 isthat the substantially planar upper and lower surfaces require only aminimum thickness of intermediary material, such as an adhesive layer,to achieve the planarization associated with firmly and uniformlylaminating the structure to additional material sheets such as glass orbarrier film. Typical thicknesses for intermediary materials are lessthan 250 micrometer. Thick intermediary materials (typically thickerthan 250 micrometers) required for higher aspect ratios structure suchas “string and tab” arrangements can be avoided. This leads to reducedmaterial cost and more efficient processing options.

Further, one notes that the structure of the integrated array of FIG. 56remains highly flexible. This permits the array to be further processedusing techniques, such as roll lamination, which operate best when oneof the material feed streams is flexible. For example a process of rolllamination of the FIG. 56 structure to a glass support/barrier sheet isdepicted in FIG. 61 and more thoroughly discussed below. There the glassmay be fed as a rigid member while the FIG. 56 structure andintermediary adhesive are fed as flexible layers to the nip of a rolllaminator.

Finally, one notes that the FIG. 56 structure involves firm positioningand interconnection of the individual cells relative each other. Therobust seaming of the films associated with adjacent cells ensures thatthe permanent positioning and interconnection is maintained despitemanipulations and handling associated with subsequent processing. Thispermits major expansion of design and form factor choices for finalmodules of the instant invention. In comparison, prior to finallamination “string and tab” legacy structures are flimsy and vulnerableto damage.

One also will appreciate that using the conductive pattern of tracesjoined by a connecting trace of material 128 as shown if FIG. 29 allowsfor substantial redundancy in current collection and contact. Should anyof the traces become electrically disabled alternate electrical pathsare readily available to accomplish the necessary current transport andcontacts.

Turning now to FIGS. 57 and 58 there is shown there a valuable featureof the modular arrays as depicted in FIG. 56. FIG. 57 is a top plan viewof a structural arrangement as depicted in FIG. 56 but with somestructural portions removed for clarity of explanation of a feature ofthe invention. FIG. 58 is a sectional view taken substantially from theperspective of lines 58-58 of FIG. 57. In FIG. 57, a pair of cells 10-1and 10-2 are shown positioned adjacent each other in series electricalarrangement as embodied in FIG. 56. One sees that a portion 257 of the“buss” 256 associated with the pair of cells may be designed to extendoutside the area occupied by the adjacently paired cells.

The sectional view of FIG. 58 is taken thru that portion 257. Referenceto FIG. 58 shows that one may access the buss 256 positioned betweenadjacent cells. One will therefore understand, that electricalconnections between two consecutive buss extensions can be used todetermine the electrical characteristics of individual cells afterassembly into the module format. Furthermore, the electrical connectionsbetween buss extensions allow for the identification, isolation, andrepair of shunted or shorted photovoltaic cells.

A common problem encountered with photovoltaic cells, especially thinfilm cells is that of electrical shunting or shorting from the top lightincident surface to the opposite bottom electrode. Such shunting mayresult from a number of sources including:

-   -   a. So called “thin film” photovoltaic cells often comprise a        self supporting metal foil substrate. These foil substrates        allow continuous deposition and manufacture of the raw PV        materials. These PV layers may be deposited over relatively        broad surfaces of the underlying metal foil substrate. The PV        material layers are often very thin (of the order 1 micron). One        problem encountered here is the surface roughness of the        supporting metal foil. This foil roughness can be greater than        the thickness of the deposited semiconductor materials. In this        situation, metal portions may protrude through the PV layers and        effectively electrically connect the top and bottom electrodes.        While various efforts are made to “smooth” the supporting metal        foil, the roughness problem may remain.    -   b. The “thin film” PV deposits may also have discontinuities        such as pinholes extending through the thickness. These may        result from a number of sources such as insufficient substrate        cleaning or flaking and scratching during handling of the raw,        unprotected PV material prior to encapsulation. It is common to        apply a conductive silver containing ink to the light incident        surface of cells to function as a current collecting structure.        The ink, when extending over a sufficiently large discontinuity        in the PV material, may wick down to the underlying metal        substrate and result in a short.    -   c. In the case of a laminated electrode such as that taught in        U.S. Pat. No. 7,635,810, a separately prepared grid is laminated        to the light incident surface of a PV cell. Because of the        reduced thickness of thin film PV materials, it is possible to        cause “punch through” of the grid from the top surface to the        underlying foil substrate during the heat and pressure exposure        encountered during the lamination process.

Such shunting or shorting causes deterioration in the performance of thecell, normally lowering both the open circuit voltage (Voc) and theshort circuit current (Isc). Unfortunately, it is difficult to detectand isolate shunts prior to the application of the collection gridstructure.

A shunt or short may often comprise a very minute contact of conductivematerial extending through the semiconductor body. Since the observedshunts or shorts often involve minimal point contacts, it has beenobserved that passing an electrical current through the shunted cellfrom front to back electrodes heats up the short sufficiently to “burnit out” (much like a fuse burns out as a result of a short circuit).Alternately, heating up the region of the short may at least “disturb”it enough to separate the point contact. One will readily understand,that the exposed buss extensions as shown in FIGS. 57 and 58 providecontacts to pass the electrical current.

One can measure the electrical resistance through a PV cell byconnecting the leads of an ohmmeter to the opposite electrodes of acell. When this is done under “dark” conditions, (no illumination), theresistance determined is hereby defined as the “dark series resistance”and abbreviated as “Rd”. For example, Rd can be conveniently determinedby placing the light incident surface of a cell against an opaquesurface such as a wood table surface and measuring the resistance. Inthe case of a CIGS cell supported by a metal foil substrate, thepositive pole of the ohmmeter is connected to the foil and the “common”or negative connected to the top electrode.

It has been observed that, for cells having a surface area of about 8square inches, a shunted or shorted cell is quickly identified if the“dark series resistance” Rd of the cell falls below about 2 ohms (i.e. 2ohms, 1 ohm, 0.5 ohm). Cells showing an Rd above about 5 ohms (i.e. 5ohms, 10 ohms, 20 ohms, 50 ohms, 75 ohms) typically performsatisfactorily. Thus, concern is raised when the Rd falls below about 5ohms. However, selected cells having Rd below 5 ohms have on occasionshown adequate performance, indicating that other parameters may, atleast partially, overcome the negative affects of partial shunting.

The use of exposed buss extensions to pass current and repair shorted orshunted cells was reduced to practice in San Jose, Calif. in August,2009. First, a number of “laminated cell stock” samples were preparedusing CIGS material supported on a stainless steel substrate. Thesesamples were prepared according to the teachings associated with FIG.55. Table A gives the data observed for the individual cells after theinitial lamination of the grids to the top surface of the cells:

TABLE A Cell # Rd After Initial Lamination 3-24 96 3-8 122 3-2 106 2-20103

These cells were then assembled into a “4-up” modular array in a fashionas depicted in FIG. 56. Table B provides the data observed followingthis array lamination:

TABLE B Cell # Rd of Cell 3-24 0.5 3-8 0.6 3-2 93. 2-20 91.

Cells 3-24 and 3-8 had thus shorted during the array lamination.Measurements of the modular array in the sun across the entire arrayshowed an open circuit voltage of 2.1 volts and a closed circuit currentof 1.51 amps. This showed that despite two cells (3-24 and 3-8) being“shunted”, the array performance had not suffered catastrophically.

The process to repair the cells involved connecting a wire probe to eachpole of a fresh 9-volt battery. These probes were then placed in contactwith the opposite electrodes of each of the shorted cells. The positivebattery pole was placed in contact with the bottom cell electrode(stainless steel) and the negative battery electrode was contacted tothe top grid electrode of the cell. It was observed that the initialcurrent across the shorted cells was 5-6 amps but it quickly droppedbelow 1 amp after about 10 seconds. Both cells 3-8 and 3-24 were treatedin this way. It should be noted that no electrical treatment was givento cells 3-2 and 2-20. Upon completion of this electrical exposure, thefollowing measurements were made:

TABLE C Cell # Rd 3-24 30.5 3-8 99.5 3-2 90. 2-20 95.The electrical measurements indicated that the shorts had been removedfrom the cells 3-24 and 3-8. In addition, it was observed that theprecise location of the original shorts could be observed by smallbubbling of the plastic around the short and even a tiny burn mark onthe backside stainless surface. It is apparent that forcing a currentthrough the original short acted to remove the short by disturbing it,possibly either by “burning it out” like a fuse or by simply melting theplastic film. The “repaired” array had electrical performance virtuallyidentical to an array never having shorts. These electrical measurementsare reported in Table D.

TABLE D Readings were taken in the sun, Aug. 18, 2009, San Jose,approximately 2:00 PM. A slight haze existed. Initial readings Voc -2.20 V Isc - 1.58 amps. Readings after a poroximately ½ hour sun soak(cells very warm) Voc - 2.12 Isc - 1.56 amps. Readings after cells hadcooled down from sun soak Voc - 2.24 V Isc - 1.53 amps.

The embodiments of FIGS. 50 through 52 show structure of “fingers” and“busses”. Other geometrical forms are clearly possible. This isespecially the case when considering structure for contacting the rearor bottom surface 66 of a photovoltaic cell 10. One embodiment of analternate structure is depicted in FIGS. 53 and 54. FIG. 53 is a topplan view while FIG. 54 is a sectional view taken substantially from theperspective of lines 54-54 of FIG. 53. In FIGS. 53 and 54, there isdepicted an article 275 analogous to article 250 of FIG. 50. The article275 in FIGS. 53 and 54 comprises “fingers” 280 similar to “fingers” 254of the FIG. 50 embodiment. However, the pattern of material 251 formingthe structure on the surface 238 a of article 275 is considerablydifferent than the “fingers” 252 and “buss” 256 of the FIG. 70embodiment. In FIG. 53, material 251 a is deposited in a mesh-likepattern having voids 276 leaving multiple regions of surface 238 aexposed. Lamination of such a structure may result in improved surfacearea contact of the pattern compared to the finger structure of FIG. 50.It is emphasized that since surface 238 a of article 275 eventuallycontacts rear surface 66 of the photovoltaic cell, potential shading isnot an issue and thus geometrical design of the exposed contactingsurfaces 238 a relative to the mating conductive surfaces 66 can beoptimized without consideration to shading issues.

Using a laminating approach to secure the conductive grid materials to aconductive surface involves some design and performance “tradeoffs”. Forexample, if the electrical trace or path “finger” 84 comprises a wireform, it has the advantage of potentially reducing light shading of thesurface (at equivalent current carrying capacity) in comparison to asubstantially flat electrodeposited, printed or etched foil member.However, the relatively higher profile for the wire form must beaddressed. It has been taught in the art that wire diameters as small as50 micrometers (0.002 inch) can be assembled into grid likearrangements. Thus when laid on a flat surface such a wire would projectabove the surface 0.002 inches. For purposes of this instantspecification and claims, a structure projecting above a surface lessthan 0.002 inches will be defined as a low-profile structure. Often alow profile structure may be further characterized as having asubstantially flat surface.

A potential cross sectional view of a wire 84 d laminated to a surfaceby the process such as that of FIG. 21 is depicted in FIG. 59. FIG. 60depicts a typical cross sectional view of an electrical trace 84 eformed by printing, electrodeposition, chemical “electroless” plating,foil etching, masked vacuum deposition etc. It is seen in FIG. 59 thatbeing round the wire itself contacts the surface essentially along aline (normal to the paper in FIG. 59). In addition, the sealing materialforming surface 80 d of film 70 may have difficulty flowing completelyaround the wire, leaving voids as shown in FIG. 59 at 99, possiblyleading to insecure contact. Another problem is that material formingsurface 80 d may flow under the wire preventing conductive contact.Thus, the thickness of the sealing layer, lamination parameters,material choice and initial projection of the wire form above thesubstrate surface become very important when using a round wire form.

On the other hand, using a lower profile substantially flat conductivetrace such as depicted in FIG. 60 increases contact surface areacompared to the line contact associated with a wire. The low profileform of FIG. 60 facilitates broad surface contact and secure laminationbut comes at the expense of increased light shading. The low profile,flat structure does require consideration of the thickness of the“flowable” sealing layer forming surface 80 e relative to the thicknessof the conductive trace. Excessive thickness of certain sealing layermaterials might allow relaxation of the “blanket” pressure promotingcontact of the surfaces 98 with a mating conductive surface such as 59.Insufficient thickness may lead to voids similar to those depicted forthe wire forms of FIG. 59. However, it has been found that, when usinglow profile traces such as embodied in FIG. 60 sealing layer thicknessesfor ranging from 0.5 mil, (0.0005 inch) to 10 mil (0.01 inch) allperform satisfactorily. Thus a wide range of sealing layer thickness ispossible, and the invention is not limited to sealing layer thicknesseswithin the stated tested range.

A low profile structure such as depicted in FIG. 60 may be advantageousbecause it may allow minimizing sealing layer thickness and consequentlyreducing the total amount of functional groups present in the sealinglayer. Such functional groups may adversely affect solar cellperformance or integrity. Also, processing speed may be increased andcost may be reduced. For example, it may be advantageous to limit thethickness of a sealing layer to 5 mils or less.

Electrical contact between conductive grid “fingers” or “traces” 84 anda conductive surface (such as cell surface 59) may be further enhancedby coating a conductive adhesive formulation onto “fingers” 84 andpossibly “busses” 86 prior to or during the lamination process such astaught in the embodiment of FIG. 21. In a preferred embodiment, theconductive adhesive would be a “hot melt” material. A “hot melt”conductive adhesive would melt and flow at the temperatures involved inthe laminating process 92 of FIG. 21. In this way surface 98 is formedby a conductive adhesive resulting in secure adhesive and electricaljoining of grid “fingers” 84 to a conductive surface such as top surface59 following the lamination process. In addition, such a “flowable”conductive material may assist in reducing voids such as depicted inFIG. 57 for a wire form. In addition, a “flowable” conductive adhesivemay increase the contact area for a wire form 84 d.

In the case of a low profile form such as depicted in FIG. 60, theconductive adhesive may be applied by standard registered printingtechniques. However, it is noted that a conductive adhesive coating fora low profile conductive trace may be very thin, of the order of 1-10micron thick. Thus, the intrinsic resistivity of the conductive adhesivecan be relatively high, perhaps up to or even exceeding about 100ohm-cm. This fact allows reduced loading and increased choices for aconductive filler. Since the conductive adhesive does not require heavyfiller loading (i.e. it may have a relatively high intrinsic resistivityas noted above) other unique application options exist.

For example, a suitable conductive “hot melt” adhesive may be depositedfrom solution onto the surface of the “fingers” and ‘busses” byconventional paint electrodeposition techniques. Alternatively, should acondition be present wherein the exposed surface of fingers and bussesbe pristine (no oxide or tarnished surface), the well knowncharacteristic of such a surface to “wet” with water based formulationsmay be employed to advantage. A freshly activated or freshlyelectroplated metal surface will be readily “wetted” by dipping in awater-based polymer containing fluid such as a latex emulsion containinga conductive filler such as carbon black. Application selectivity wouldbe achieved because the exposed polymeric sealing surface 80 would notwet with the water based latex emulsion. The water based material wouldsimply run off or could be blown off the sealing material using aconventional air knife. However, the water based film forming emulsionwould cling to the freshly activated or electroplated metal surface.This approach is similar to applying an anti-tarnish or conversion dipcoating to freshly electroplated metals such as copper and zinc.

Alternatively, one may employ a low melting point metal-based materialas a constituent of the material forming either or both surfaces 98 and100 of “fingers” and “busses”. In this case the low melting pointmetal-based material, or alloy, is caused to melt during the temperatureexposure of the process 92 of FIG. 21 (typically less than 600 degreesF.) thereby increasing the contact area between the mating surfaces 98,100 and a conductive surface such as 59. Such low melting pointmetal-based materials may be applied by electrodeposition or simpledipping to wet the underlying conductive trace. Suitable low meltingpoint metals may be based on tin, such as tin-bismuth and tin-leadalloys. Such alloys are commonly referred to as “solders”. In anotherpreferred embodiment indium or indium containing alloys are chosen asthe low melting point contact material at surfaces 98, 100. Indium meltsat a low temperature, considerably below possible laminationtemperatures. In addition, indium is known to bond to glass and ceramicmaterials when melted in contact with them. Given sufficient laminationpressures, only a very thin layer of indium or indium alloy would berequired to take advantage of this bonding ability.

In yet another embodiment, one or more of the layers 84, 86, 88, 90 etc.may comprise a material having magnetic characteristics. Magneticmaterials include nickel and iron. In this embodiment, either a magneticmaterial in the cell substrate or the material present in thefinger/grid collector structure is caused to be permanently magnetized.The magnetic attraction between the “grid pattern” and magneticcomponent of the foil substrate of the photovoltaic cell (or visa versa)creates a permanent “pressure” contact.

In yet another embodiment, the “fingers” 84 and/or “busses” 86 comprisea magnetic component such as iron or nickel and a external magneticfield is used to maintain positioning of the fingers or busses duringthe lamination process depicted in FIG. 21.

A number of methods are available to employ the current collecting andinterconnection structures taught hereinabove with photovoltaic cellstock to achieve effective interconnection of multiple cells intoarrays. A brief description of some possible methods follows. A firstmethod envisions combining photovoltaic cell structure with currentcollecting electrodes while both components are in their originallyprepared “bulk” form prior to subdivision to dimensions appropriate forindividual cells. A expansive surface area of photovoltaic structuresuch as embodied in FIGS. 1 and 2 of the instant specificationrepresenting the cumulative area of multiple unit cells is produced. Asa separate and distinct operation, an array comprising multiple currentcollector electrodes arranged on a common substrate, such as the arrayof electrodes taught in FIGS. 9 through 15 is produced. The bulk arrayof electrodes is then combined with the expansive surface ofphotovoltaic structure in a process such as the laminating processembodied in FIG. 21. This process results in a bulk combination ofphotovoltaic structure and collector electrode. Appropriate subdividingof the bulk combination results in individual cells having a preattachedcurrent collector structure. Electrical access to the collectorstructure of individual cells may be achieved using through holes, astaught in conjunction with the embodiments of FIGS. 35 through 42.Alternatively, one may simply lift the collector structure away from thecell surface 59 at the edge of the unit photovoltaic cell to expose thecollector electrode.

Another method of combining the collector electrodes and interconnectstructures taught herein with photovoltaic cells involves a first stepof manufacture of multiple individual current collecting structures orelectrodes. A suitable method of manufacture is to produce a bulkcontinuous roll of electrodes using roll to roll processing. Examples ofsuch manufacture are the processes and structures embodied in thediscussion of FIGS. 9 through 15 of the instant specification. The bulkroll is then subdivided into individual current collector electrodes forcombination with discrete units of cell stock. The combination producesdiscrete individual units of “tabbed” cell stock. In concept, thisapproach is appropriate for individual cells having known and definedsurface dimensions, such as 6″×6″, 4″×3″, 2″×8″ and 2″×16″. Cells ofsuch defined dimensions may be produced directly, such as withconventional single crystal silicon manufacture. Alternatively, cells ofsuch dimension are produced by subdividing an expansive cell structureinto smaller dimensions. The “tabbed” cell stock thereby produced may bepackaged in cassette packaging. The discrete “tabbed” cells are thenelectrically interconnected into an array, optionally using automaticcassette dispensing, positioning and electrical joining of multiplecells. The overhanging tabs of the individual “tabbed” cells facilitatesuch joining into an array as was taught in the embodiments of FIGS. 24,34, 43, and 56 above

Alternate methods to achieve interconnected arrays according to theinstant invention comprise first manufacturing multiple currentcollector structures in bulk roll to roll fashion. In this case the“current collector stock” would comprise electrically conductive currentcollecting structure on a supporting sheetlike web essentiallycontinuous in the “Y” or “machine” direction. Furthermore, theconductive structure is possibly repetitive in the “X” direction, suchas the arrangement depicted in FIGS. 9, 12 and 38 of the instantspecification. In a separate operation, individual rolls of unit “cellstock” are produced, possibly by subdividing an expansive web of cellstructure. The individual rolls of unit “cell stock” are envisioned tobe continuous in the “Y” direction and having a defined widthcorresponding to the defined width of cells to be eventually arranged ininterconnected array.

Having separately prepared rolls of “current collector stock” and unit“cell stock”, multiple array assembly processes may be considered asfollows. In one form of array assembly process, a roll of unit “currentcollector stock” is produced, possibly by subdividing a bulk roll of“current collector stock” to appropriate width for the unit roll. Therolls of unit “current collector stock” and unit “cell stock” are thencombined in a continuous process to produce a roll of unit “tabbedstock”. The “tabbed” stock therefore comprises cells, which may beextensive in the “Y” dimension, equipped with readily accessiblecontacting surfaces for either or both the top and bottom surfaces ofthe cell. The “tabbed” stock may be assembled into an interconnectedarray using a multiple of different processes. As examples, two suchprocess paths are discussed according to (A) and (B) following.

Process Example (A)

Multiple strips of “tabbed” stock are fed to a process such that aninterconnected array of multiple cells is achieved continuously in themachine (original “Y”) direction. This process would produce aninterconnected array having series connections of cells whose numberwould correspond to the number of rolls of “tabbed” stock being fed. Inthis case the individual strips of “tabbed” stock would be arranged inappropriate overlapping fashion as dictated by the particular embodimentof “tabbed” stock. The multiple overlapping tabbed cells would beelectrically joined appropriately using electrical joining means,surface mating through laminating or combinations thereof as has beentaught above. Both the feed and exit of such an assembly process wouldbe substantially in the original “Y” direction and the output of such aprocess would be essentially continuous in the original “Y” direction.The multiple interconnected cells could be rewound onto a roll forfurther processing.

Process Example (B)

An alternative process is taught in conjunction with FIGS. 61 and 62.FIG. 61 is a top view of the process and FIG. 62 is a perspective view.The process is embodied in FIGS. 61 and 62 using the “tabbed cell stock”270 as shown in FIG. 55. One will recognize that other forms of “tabbedcell stock” such as those shown in FIGS. 23, 33, 42, are also suitable.A single strip of “tabbed” cell stock 270 is unwound from roll 300 andcut to a predetermined length “Y-61”. “Y-61” represents the width of theform factor of the eventual interconnected array. Strips of “tabbed cellstock” cut to length “Y-61” may then be processed according to alternateprocessing sequences. In a first sequence as embodied in FIGS. 61 and 62the cut strip is directly positioned for further interconnecting intothe modular array. In another sequence the strips of length “Y-61” areaccumulated in feeder cassettes and then fed to the modularizationprocess from the cassettes. A possible advantage to the cassettingapproach is that the individual cut strips may be performance evaluatedand matched prior to assembly into an interconnected module.

In either of these sequences, a first step in the interconnectionprocess secures a cut strip in position. In the process embodiment ofFIGS. 61 and 62, this positioning is accomplished using a vacuum belt302. The strip is then “shuttled” in the original “x” direction of the“tabbed cell stock” a distance substantially the length of a repeatdimension among adjacent series connected cells. This repeat distance isindicated in FIGS. 56 and 61 as “X-10”. A second strip of “tabbed cellstock” 270 is then appropriately positioned to properly overlap thefirst strip, as best shown in FIG. 56. The second strip is then slightlytacked to the first strip of “tabbed cell stock” using exposed substratematerial, such as that indicated at numeral 306 in FIG. 56. The tackingmay be accomplished quickly and simply at points spaced in the “Y-61”direction using heated probes to melt small regions of the sealingmaterial forming the surface of the exposed substrate. It is understoodthat other methods of relative positioning of tabbed cell strips, suchas adhesive application or spot welding, may be chosen to maintainpositioning of the adjacent cells.

This process of positioning and tacking is repeated multiple times.Normally, the repetitively positioned cell structures are passed througha “fixing” step to accomplish completion of the structural andelectrical joining of the modular arrangement. The electrical joiningmay take many forms, depending somewhat on the structure of theindividual “tabbed cell stock”. For example, in the embodiment of FIGS.24 and 25, joining may take the form of an electrically conductiveadhesive, solder, etc. as previously taught. In the case of “tabbed”cell stock 270 such as embodied in FIG. 55, electrical joining maycomprise a simple “blanket hold down” of conductive structure resultingfrom adhesive lamination such as previously described and embodied inFIG. 56.

The “fixing” step may involve heat and or pressure and is oftenaccomplished using roll, vacuum, or press lamination. In the embodimentof FIGS. 61 and 62, the “fixing” is accomplished using lamination withroll laminator 310. Thus the series connected structure 290 depicted inFIG. 56 is achieved. It is seen that in the process depicted in FIGS. 61and 62 the interconnected cell stock would exit the basic laminationassembly process in a fashion substantially perpendicular to theoriginal “Y” direction of the “tabbed cell stock”. The interconnectedcells produced would therefore have a new predetermined width “Y-61” andthe new length (in the original “X” direction) may be of extendeddimension. The output in the new length dimension may be described asessentially continuous and thus the output of interconnected cells maybe gathered on roll 320 as shown.

It is noted that the overall process depicted in FIGS. 61 and 62 issubstantially continuous in that the feed stream to the process (tabbedcell stock 270) is continuous while the output of the process 290 mayalso be continuous. The process scheme depicted in FIGS. 61 and 62permits other options while maintaining the substantially continuousnature of the overall process. For example, should one wish to apply atransparent environmental protective layer to the modular cell array,this can easily be accomplished using an auxiliary feed stream ofbarrier film prior to the lamination depicted at rolls 310. One may alsoconsider application of a flexible backsheet in similar fashion. Inaddition, other processing options may be considered both before andafter the “fixing” depicted by lamination 310 and while the modulararray remains in it “continuous” form. These other options includeadditional lamination steps, quality checks on individual cells ormodule lengths, and spray application of functional coatings.

It will be appreciated that using the processing as embodied in FIGS. 61and 62, a large choice of final form factors for the interconnectedarray is possible. For example, dimension “Y-61” could conceivably andreasonably be quite large, for example 8 feet while dimension “X-61” maybe virtually any desired dimension. It is seen that the FIGS. 61/62process results in a repetitive arrangement of cells encapsulated andseamed together in a robust, flexible sheetlike structure. Large modulesizes can be produced which are also very easy to handle and manipulate.To date, module sizes employing “string and tab” or “shingling”interconnections have been restricted by the practical problems ofhandling and interconnecting large numbers of small individual cells.The largest commercially available “string and tab” module known to theinstant inventor is 26 square feet. Using the instant invention, modulesizes far in excess of 26 square feet are reasonable. Large modulessuitable for combination with standard construction materials may beproduced. For example, a module surface area of 4 ft. by 8 ft. (astandard dimension for plywood and other sheetlike constructionmaterials) is readily produced using the processing of the instantinvention. Alternatively, since the final modular array can beaccumulated in roll form as shown in FIGS. 61 and 62, installation couldbe facilitated by the ability to simply “roll out” the array at theinstallation site. The ability to easily make modular arrays of veryexpansive surface and having wide choice of form factor greatlyfacilitates eventual installation and is a substantial improvement overexisting options for modular array manufacture.

Finally, the ability to easily specify module dimensions allows asignificant expansion of options for pre-fabrication of modules andmodule designs at the factory.

Another significant advantage to the modular processing taught here isthe ability to quickly and easily change electrical characteristics ofthe final module. The module currents are determined in large part bythe surface area of the individual cells (length by width) which may beeasily varied. Using the depicted process, module voltages may be easilyadjusted by simply specifying the module lengths “X-61” and the width“X-10” of the individual cells.

Referring now to FIGS. 63 through 65 of this instant specification,details of a module structure according to embodiments of the instantinvention are presented. In FIG. 63, a top plan view of a portion ofphotovoltaic module 330 is depicted. In the FIG. 63 embodiment, overallmodule surface dimensions are indicated by width (Wm) and length (Lm).Typical module dimensions may be 4 ft. Wm by 8 ft. Lm. However, one willrealize that the invention is not limited to these dimensions. Modulesurface dimensions may be larger or smaller (i.e. 2 ft. by 4 ft., 4 ft.by 16 ft., 8 ft. by 4 ft., 8 ft. by 16 ft., 8 ft. by 100 ft., etc.)depending on specific requirements. Thus, the overall module may berelatively large.

The FIG. 63 depiction includes terminal ends 329 and 331 at oppositeends of module 330. Positioned adjacent the edge of the terminal end 331is electrically conductive terminal bar 334. One realizes that aterminal bar such as the region indicated as 334 in FIG. 63 may bepresent at the ends of modular arrangements such as embodied in FIGS. 43and 56. For example, a possible “terminal bar” region is shown atnumeral 339 in FIG. 42. One further understands that a terminal bar 338of polarity opposite that of 334 may be positioned at the terminal end329 opposite terminal end 331. In the embodiment of FIG. 63, throughholes 332 have been positioned within the terminal bars 334 and 338.Through holes such as those indicated by 332 may be used to achieveelectrical communication between conductive surfaces on opposite sidesof the terminal bar region. This feature expands installation designchoices and may improve overall contact between the terminal bars andconductive attachment hardware.

In the FIG. 63 embodiment, the module comprises multiple cells havingsurface dimensions of width Wcell (actually in the defined lengthdirection of the overall module) and length Lcell as shown. In the FIG.63 embodiment, the cell length (Lcell) is shown to be substantiallyequivalent to the module width (Wm). In addition, terminal bars 334 and338 are shown to span substantially the entire width (Wm) of the module.

For purposes of describing embodiments of the invention, a typicalmodule as embodied in FIG. 63 may have an overall length Lm of 8 feetand overall width Wm of 4 feet. Typically the cell width (Wcell) may befrom 0.2 inch to 12 inches depending on choices among many factors. Fordescriptive purposes a cell width (Wcell) may be considered to be 1.97inches. Using these typical dimensions the module 330 of FIG. 63comprises 48 individual cells interconnected in series, with terminalbars 334 and 338 of about 0.7 inch width at each terminal end of themodule. Assuming an individual cell open circuit voltage of 0.5 volts(typical for example of a CIGS cell), the open circuit voltage for themodule embodied in FIG. 63 would be about 24 volts. This voltage isnoteworthy in that it is insufficient to pose a significant electricalshock hazard, and further that the opposite polarity terminals areseparated by 8 feet. Should higher voltages be permitted or desired, onevery long module or multiple modules connected in series may beconsidered, employing mounting and connection structures taught hereinfor the individual modules. Alternatively, should higher voltage cellsbe employed (such as multiple junction a-silicon cells which maygenerate open circuit voltages in excess of 2 volts), the cell width(Wcell) may be increased accordingly to maintain a safe overall modulevoltage. At a ten percent module efficiency, the module of FIG. 63 asdescribed would generate about 290 Watts.

Continuing reference to FIG. 64 shows photovoltaic cells 10 d, 10 e, 10f, etc. positioned in a repetitive arrangement. In the embodiment, theindividual cells comprise thin film semiconductor material supported bya metal-based foil and modularized as taught above, for example asembodied in FIG. 43 or 56. Alternate photovoltaic cell structures knownin the art and incorporated into expansive modules would be appropriatefor practice of the invention. On the top free surface 347 of module 330in the FIG. 64 embodiment, a pattern of fingers 348 and busses 349collect power for transport to an adjacent cell in series arrangement.

FIG. 65 is a sectional depiction from the perspective of lines 65-65 ofFIG. 64. The FIG. 65 embodiment shows a series connected arrangement ofmultiple photovoltaic cells 10 d, 10 e, 10 f, etc. To promote clarity ofpresentation, the details of the series connections and cell structureare not shown in FIG. 65. One will realize that FIG. 65 is a greatlysimplified depiction of series connected structures such as those ofFIGS. 24, 34, 43, and 56.

One realizes the module structures depicted in FIG. 65 may be readilyfabricated at a factory and shipped in bulk packaging form to aninstallation site. Alternatively, additional components may beincorporated at the factory prior to shipment. For example, it may beappropriate to apply a transparent protective barrier over the topsurface 347 of module 330. Transparent protective layers may be eitherrigid or flexible. Rigid glass sheets have been commonly used astransparent barriers for photovoltaic modules. An alternative to rigidglass may be very thin flexible glass materials such as those identifiedas Corning 0211 and Schott D263. More recently expansive area, flexibletransparent barrier sheets have been proposed to allow production offlexible, environmentally secure photovoltaic modules. These barriersheets may typically comprise stacks of multiple films in a laminarstructure. The films may comprise multiple inorganic layers orcombinations of multiple organic and inorganic layers. The multiplelayers present a tortuous path for moisture or gas molecules topenetrate through the barrier sheet. The individual layers of thebarrier sheet are typically very thin, often of the order of onemicrometer or less, formed by various processing such as sputtering,chemical vapor deposition and atomic layer deposition. Thus theseindividual layers are typically not self supporting. A barrier stack ofmultiple thin polymer and inorganic pairs (dyads) may be applieddirectly to a device to be protected. Alternatively, the barrier stackmay be deposited onto a supporting carrier film which itself may beapplied over a device for protection. An example of such a barrier filmtechnology is that marketed by Vitex Systems under the tradename“Barix”.

FIG. 66 is a side view depicting a roll lamination of modular structure330 to transparent protective or barrier layer 333. It is understoodthat other lamination techniques such as vacuum lamination may beappropriate. Since module 330 is flexible the application of either arigid barrier layer such as glass or a flexible barrier film may beaccomplished using roll lamination such as depicted in FIG. 66. Glasssheets would normally be considered rigid. Polymer sheets may beflexible or rigid Sheet 333 may also comprise multiple additional layersimparting various functional attributes such as structural processingstrength, environmental barrier protection, adhesive characteristics andUV resistance, abrasion resistance, and cleaning ability.

As one understands, the roll lamination depicted in FIG. 66 may havemanufacturing benefits compared to other lamination processes such asvacuum lamination. In the roll lamination process of FIG. 66,appropriate heat and pressure causes adhesive/sealant 335 tosufficiently soften and flow to form a seal between the facing surfacesof the module 330 and sheet 333. Rolls 337 squeeze the warmed compositetogether to form this surface seal while at the same time expelling amajority of air. In this process the sheets may be preheated prior toentering the rolls or the rolls themselves may be heated to sufficientlysoften the sealant 335. Adhesive or sealant 335 may comprise a number ofsuitable materials, including thermoplastic or thermosetting materials,pressure sensitive adhesive formulations, ionomers, ethylene vinylacetate (EVA) formulations, polyolefins, acrylics and the like.Alternatively, the sealant 335 may comprise a pressure sensitiveadhesive and the process of FIG. 66 may be practiced at roomtemperature.

FIG. 67 is a sectional view of one embodiment of adhesive/sealant 335taken substantially from the lines 67-67 of FIG. 66. In FIG. 67, sealant335 is shown to compose multiple layers 344, 345, and 346. In thisembodiment layers 344 and 346 are formed by materials having adhesiveaffinity to the corresponding surfaces of articles 333 and 330. Furtherin this embodiment, layer 345 represents a structural carrier filmsupporting the adhesive layers 344 and 346. Such a structural carrierfilm is used when adhesive layers 344, 346 do not possess the integrityrequired for the envisioned processing. One will realize that otherembodiments are possible including a single adhesive layer absent thecarrier layer 345. One will also realize that should the top surface 347of module 330 have adhesive affinity for barrier layer 333 thenadhesive/sealant 335 may possibly be eliminated.

It is understood that once the module is applied to transparent sheet333, the composite will behave mechanically similar to the transparentsheet. Should sheet 333 be rigid, as is typical for glass or a thickplastic sheet, the composite (module 330/sealant 335/transparent sheet333) would be characterized as rigid. Should sheet 333 be flexible, asis typical for many plastic barrier materials, the composite will remainflexible.

It is emphasized that the roll lamination process depicted in FIG. 66 isbut one form of process capable of creating the(module/sealant/transparent barrier sheet) structure. Other laminationtechniques, such as vacuum lamination or simple spreading of sealingmaterial followed by transparent sheet application, may be alternativelyemployed. In some embodiments, adhesive/sealant 335 may be eliminatedand sheet 333 may simply cover module 330. In other embodiments, barrierlayer 333 may be applied by liquid flow coating or spraying of themodule 330.

The sectional view of FIG. 68 embodies structure which may result fromthe process depicted in FIG. 66. In FIG. 68, cells 10 d, 10 e, 10 f areinterconnected in series and the arrangement is laminated to barrier 333through adhesive/sealant layer 335 as shown. Each cell has a lightincident surface 59 overlayed by its own distinctive laminated unit ofinterconnecting structure. The unit of interconnecting structurecomprises a collector portion having electrical trace material 266positioned on surface 240 of substrate 230 as has been previouslyembodied herein. In the FIG. 68 embodiment, substrate 230 comprisesthree layers, 232, 234, 236. Layer 236 forming surface 240 comprisesmaterial having adhesive affinity for the light incident surfaces 59 ofphotovoltaic cells 10. Layer 232 forming surface 238 comprises materialhaving adhesive affinity of the bottom conductive surface 66 of cell 10.Sandwiched between layers 232 and 236 is layer of structural polymer234. One readily realizes that the stack 232/234/236 is translucent ortransparent since it overlays the light incident surface of the cells.

Structural polymer support layer 234 may serve multiple functions.First, it may serve as a supporting layer for layers of material 232 and236. Often these layers 232 and 236 are formulated for adhesive affinitybut may suffer from a lack of structural integrity, being thin or havinglow modulus. This condition is often present in laminating films.Second, the structural layer may be important for facile processing ofthe substrate through various processing steps. In addition, thestructural layer 234 may supply a protective film to protect the cellsurfaces from abrasion and chafing from the handling through the variousprocess steps. Finally, the structural layer normally exhibits arelatively high elastic modulus, which contributes to firm “blanket”holddown of the electrical traces to the cell surface followinglamination. The firm holddown achieved with the high modulus structurallayer contributes to excellent thermal cycling and aging performance ofthe composites of the invention.

It is understood that layer 234 may in practice represent a multiplelayer structure. As has previously been taught the multiple layers mayprovide additional functional benefits such as environmental barrierproperties, uv resistance, cut resistance, electrical insulatingproperties etc.

Inspection of the structure embodied in FIG. 68 reveals that eachindividual cell has its light incident surface 59 overlayed by its ownindividual and distinct portion of unit of interconnecting structure.Specifically, a cell such as 10 d is overlayed by a unit ofinterconnecting structure comprising layer portions 232 d, 234 d, 236 d.In particular, one will recognize that the polymer support layer 234 doverlaying a first cell 10 d is separate, distinct, spaced apart, anddisconnected from the polymer support layer 234 e overlaying a secondcell 10 e. Similarly, layer 232 d is separate and disconnected fromlayer 232 e, while layer 236 d is separate and disconnected from layer236 e. Continued reference to FIG. 68 shows that these same structuraldistinctions exist for those portions of unit of interconnectingstructure contacting the bottom surfaces 66 of cells 10. For example,layer 232 e contacting the bottom surface 66 of cell 10 d is separate,spaced apart, and disconnected from layer 232 f contacting the bottomsurface 66 of cell 10 e. Similarly, polymer support layer 234 e coveringthe bottom surface 66 of cell 10 d is separate, spaced apart anddisconnected from polymer support layer 234 f covering the bottomsurface 66 of cell 10 e.

Continued reference to FIG. 68 shows adhesive layer 335 positioned abovethe series arrangement of multiple cells. As seen in the embodiment, theadhesive layer extends as a continuous structure to cover a multiple ofcells. As previously noted, adhesive layer 335 may be a single layer orbe a composite of multiple laminated layers. Positioned above adhesivelayer 335 is environmental barrier 333. Barrier 333 may comprise glassor a flexible barrier sheet.

The module structure embodied in FIG. 68 may also include a protectivebackside barrier (not shown) commonly referred to as a “backsheet”.Suitable “backsheets” are known in the art. Typical “backsheets” maycomprise glass or laminated sheets combining metal foil and polymer filmlayers. Since they are applied to the backside of the photovoltaic cell,the “backsheet” need not be transparent. In addition, flexiblebacksheets of polymer/metal foil laminates may be applied to thestructures of the invention by techniques taught hereinbefore. Forexample, a flexible backsheet may be applied during the process of FIGS.61,62 at laminating rolls 310. Alternatively, a flexible “backsheet” maybe applied by the processing embodied in FIG. 66.

The invention contemplates a particularly attractive conductive joiningthat may be achieved through a technique described herein as a laminatedcontact. In light of the teachings to follow one will recognize that thestructures shown in FIGS. 9-15 and 16-20 may function and be furthercharacterized as electrodes employing a laminated contact (laminatingelectrodes). One structure involved in the laminated contact is a firstportion of conductive structure which is to be electrically joined to asecond conductive surface. The first portion comprises a conductivepattern positioned over or embedded in a surface of an adhesive. In apreferred embodiment, the adhesive is characterized as a polymeric hotmelt adhesive. A hot melt adhesive is a material, substantially solid atroom temperature, whose full adhesive affinity is activated by heating,normally to a temperature where the material softens or meltssufficiently for it to flow under simultaneously applied pressure. Manyvarious hot melt materials, such as acrylics and ionomers, are wellknown in the art. It is noted that while the invention is describedherein regarding the use of hot melt laminating adhesives, the inventioncontemplates use of laminating adhesives such as pressure sensitiveadhesives not requiring heat for function. In addition, the inventioncontemplates the use of cross-linkable adhesive formulations. Suchformulations exhibit adhesive tack or “bite” prior to cross-linking.They are thus applied to a surface prior to cross-linking. Afterapplication, heating and optionally pressure causes a reaction toproduce bonding between the polymer chains. Such heat and pressure maybe applied during a laminating stage of the present invention. This“thermosetting” reaction eliminates polymer flow but results insubstantial increases in elasticity and strength. One of course realizesthat cross-linking prior to application would prevent flow and surfacewetting and thereby render the material useless as an adhesive.

In the process of producing a laminated contact, the exposed surface ofa conductive material pattern positioned on or embedded in the surfaceof an adhesive is brought into facing relationship with a secondconductive surface to which electrical joining is intended. Heat and/orpressure are applied to soften the adhesive which then may flow aroundedges or through openings in the conductive pattern to also contact andadhesively “grab” the exposed second surface portions adjacent theconductive pattern. When heat and pressure are removed, the adhesiveadjacent edges of the conductive pattern firmly fixes features ofconductive pattern in secure mechanical contact with the second surface.

The laminated contact is particularly suitable for the electricaljoining requirements of many embodiments of the instant invention. Asimplified depiction of structure to assist understanding the concept ofa laminated contact is embodied in FIGS. 69 and 70. FIG. 69 shows a topplan view of an article 350. Article 350 comprises a conductive mesh 352positioned on the surface of or partially embedded in adhesive 351. Mesh352 may be in the form of a metal screen, a metallized fabric or afabric comprising conductive fibers and the like. Adhesive 351 possessesadhesive affinity to the conductive surface to which electrical joiningis intended. Numeral 354 indicates holes through the mesh or fabric. Onewill realize that many different patterns and conductive materials maybe suitable for the conductive material represented by conductive mesh352, including conductive comb-like patterns, serpentine traces,monolithic metal mesh patterns, metallized fabric, wires, etched or diecut metal forms, forms comprising vacuum deposited, chemically depositedand electrodeposited metals, etc.

FIG. 70 shows a sectional view of article 350 juxtaposed such that thefree surface of adhesive 351 and metal 352 are in facing relationship toa mating conductive surface 360 of article 362 to which electricaljoining is desired. In the embodiment, article 350 is seen to be acomposite of the conductive material pattern 352 positioned on a topsurface of hot melt adhesive film 351. In the embodiment, an additionalsupport film 366 is included for structural and process integrity, andpossibly barrier properties. Additional film 366 may be a polymer filmof a material such as polyethylene terephthalate, polyethylenenaphthalate (PEN), polypropylene, polycarbonate, etc. Film 366 may bemultilayered and comprise layers intended to achieve functionalattributes such as moisture barrier, UV protection etc. Film 366 mayalso comprise a structure such as glass. Article 350 can includeadditional layered materials (not shown) to achieve desired functionalcharacteristics similar to article 70 discussed above. Also depicted inFIG. 70 is article 362 having a bottom surface 360. Surface 360 mayrepresent, for example, the top or bottom surfaces 59 or 66 respectivelyof solar cell structure 10 (FIG. 2A).

In order to achieve the laminated contact, articles 350 and 362 arebrought together in the facing relationship depicted and heat andpressure are applied. The adhesive layer 351 softens and flows tocontact surface 360. In the case of the FIG. 70 embodiment, flow occursthrough the holes 354 in the mesh 352. Upon cooling and removal of thepressure, the metal mesh 352 overlays and is held in secure and firmelectrical contact with surface 360 by virtue of the adhesive bondbetween adhesive 351 and surface 360. Thus mesh may function as alaminated electrode or current collector in combination with surface360.

Example 1

A standard plastic laminating sheet from GBC Corp. 75 micrometer (0.003inch) thick was coated with DER in a pattern of repetitive fingersjoined along one end with a busslike structure resulting in an articleas embodied in FIGS. 16 through 19. The fingers were 0.020 inch wide,1.625 inch long and were repetitively separated by 0.150 inch. Thebuss-like structure which contacted the fingers extended in a directionperpendicular to the fingers as shown in FIG. 16. The buss-likestructure had a width of 0.25 inch. Both the finger pattern andbuss-like structure were printed simultaneously using the same DER inkand using silk screen printing. The DER printing pattern was applied tothe laminating sheet surface formed by the sealing layer (i.e. thatsurface facing to the inside of the standard sealing pouch).

The finger/buss pattern thus produced on the lamination sheet was thenelectroplated with nickel in a standard Watts nickel bath at a currentdensity of 50 amps. per sq. ft. Approximately 4 micrometers of nickelthickness was deposited to the overall pattern.

A photovoltaic cell having surface dimensions of 1.75 inch wide by2.0625 inch long was used. This cell was a CIGS semiconductor typedeposited on a 0.001 inch stainless steel substrate. A section of thelaminating sheet containing the electroplated buss/finger pattern wasthen applied to the top, light incident side of the cell, with theelectroplated grid finger extending in the width direction (1.75 inchdimension) of the cell. Care was taken to ensure that the buss region ofthe conductive electroplated metal did not overlap the cell surface.This resulted in a total cell surface of 3.61 sq. inch. (2.0625″×1.75″)with about 12% shading from the grid, (i.e. about 88% open area for thecell).

The electroplated “finger/buss” on the lamination film was applied tothe photovoltaic cell using a standard Xerox office laminator. Theresulting completed cell showed good appearance and connection.

The cell prepared as above was tested in direct sunlight forphotovoltaic response. Testing was done at noon, Morgan Hill, Calif. onApr. 8, 2006 in full sunlight. The cell recorded an open circuit voltageof 0.52 Volts. Also recorded was a “short circuit” current of 0.65 Amps.This indicates excellent power collection from the cell at highefficiency of collection.

Example 2

Individual thin film CIGS semiconductor cells comprising a stainlesssteel supporting substrate 0.001 inch thick were cut to dimensions of7.5 inch length and 1.75 inch width.

In a separate operation, multiple laminating collector grids wereprepared as follows. A 0.002 inch thick film of Surlyn material wasapplied to both sides of a 0.003 inch thick PET film to produce astarting laminating substrate as embodied in FIG. 44. Holes having a0.125 inch diameter were punched through the laminate to produce astructure as in FIG. 48. A DER ink was then printed on opposite surfacesand through the holes to form a pattern of DER traces. The resultingstructure resembled that depicted in FIG. 51. The grid fingers 254depicted in FIGS. 50 and 51 were 0.012 inch wide and 1.625 inch long andwere spaced on centers 0.120 inch apart in the length direction. Thegrid fingers 252 were 0.062 inch wide and extended 1 inch and werespaced on centers 0.5 inch apart. The printed film was thenelectroplated to deposit approximately 2 micrometers nickel strike, 5micrometers copper and an outer flash coating of 1 micrometer nickel.This operation produced multiple sheets of laminating current collectorstock having overall dimension of 7.5 inch length (“Y” dimension) and4.25 in width (“X” dimension) as indicated in FIG. 50. These individualcurrent collector sheets were laminated to cells having dimension of7.25 inches in length and 1.75 inches in width to produce tabbed cellstock as depicted in FIG. 55. A standard Xerox office roll laminator wasused to produce the tabbed cell stock. Six pieces of the tabbed cellstock were laminated together as depicted in FIG. 56. A standard Xeroxoffice roll laminator was used to produce the FIG. 56 embodiment. Thecombined series interconnected array had a total surface area of 76.1square inches. In full noon sunlight the 6 cell array had an opencircuit voltage of 3.2 Volts and a short circuit current of 2.3 amperes.

While many of the embodiments of the invention refer to “currentcollector” structure, one will appreciate that similar articles could beemployed to collect and convey other electrical characteristics such asvoltage.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications,alternatives and equivalents may be included without departing from thespirit and scope of the inventions, as those skilled in the art willreadily understand. Such modifications, alternatives and equivalents areconsidered to be within the purview and scope of the invention andappended claims.

1. In combination, photovoltaic cell structure and an interconnecting structure, said combination characterized as having, a first unit of photovoltaic cell structure, said unit comprising a top light incident cell surface formed by a transparent conductive material, an interconnecting structure comprising a first pattern of electrically conductive material extending over a first surface of an insulating sheetlike form, said first pattern comprising multiple parallel traces having a width less than 0.015 inch, said interconnecting structure further comprising a second pattern of electrically conductive material extending over a second surface of said insulating sheetlike form, said interconnecting structure further characterized as having a monolithic conductive material forming portions of both first and second patterns. said first pattern extending over a preponderance of said top light incident surface. 